Author: Alice Roberts

What are nature-based solutions?

13 October 2021

Sustainable bioenergy

What are nature-based solutions?

Nature-based solutions are means of removing carbon dioxide (CO2) from the atmosphere by conserving, restoring, or managing physical environments.

These are separate from engineered or technology-based solutions for removing CO2, in that they use natural forest, soil, and coastal ecosystems. A landscape that can absorb CO2 from the atmosphere and trap it there is known as a carbon sink.

How can nature-based solutions help tackle climate change?  

Reducing CO2 levels in the atmosphere is key to tackling climate change. The Paris Agreement sets out targets for organisations and nations to reduce their CO2 emissions to keep global warming within 1.5 degrees Celsius of pre-industrial levels and avoid “catastrophic” consequences.

However, even as industries strive to decarbonise, some crucial sectors of the economy, such as aviation and agriculture, may prove hugely difficult or even impossible to entirely reduce emissions to zero. Therefore, as well as reducing CO2 emissions, it will be essential to actively remove CO2 that may remain in the economy. This makes nature-based solution’s ability to absorb CO2 from the atmosphere crucially important.

Nature and carbon sinks have kept Earth’s natural carbon cycle balanced since long before humans even stood upright. And they have a crucial role to play in removing CO2 that remains in the atmosphere even as industries strive to reduce their emissions.

How can forests work as nature-based ways of capturing carbon? 

Forests remove carbon from the atmosphere using photosynthesis to capture CO2, using the carbon as a source of energy while releasing oxygen. A 2014 study found that the world’s forests had absorbed as much as 30% of annual global human-generated CO2 emissions over the previous few decades. Forests are some of the earth’s most important carbon sinks, but face threats such as creeping urbanisation. Protecting and managing forests is an important part of ensuring they continue to remove CO2 from the atmosphere.

Afforestation is the establishing of a new forest while reforestation is the restoration of a forest where trees have been lost. Afforestation and reforestation require significant planting and maintenance of trees, but offer additional benefits of reducing the chances of desertification and flooding.

Improved forest management also increases the productivity of forests with activities like thinning diseased or suppressed trees. This is because young trees absorb more CO2 to fuel their growth than more mature forests that do not grow at the same rate.

What other ways can the land capture CO2?

Forests are not the only way land can be used to remove CO2 from the atmosphere. Soil all over the Earth’s surface is a massive carbon sink. Simple changes in farming methods can better protect soil and enable it to continue serving as a sources of carbon removal and storage. Such methods include rotating crops and reviving grasslands, which create larger volumes of plant biomass that decay and store more carbon in the soil.

The effectiveness of soil as a carbon sink can be enhanced further by using a substance called biochar. Biochar is a high-carbon form of charcoal, made by burning biomass like wood or agricultural waste in a zero-oxygen environment. When this charcoal is added to soil, more of the carbon absorbed will remain locked in it.

And soil isn’t the only earth-based natural substance that absorbs CO2 – rocks can, too. As they are rained on, weather and erode, rocks naturally absorb carbon. The bicarbonate that is produced is washed into the sea and is eventually stored on the seabed. This process can be enhanced by grinding rock into powder and spreading it over a large area.

How can restoring environments remove carbon?  

Mangroves on coasts and riverbanks, as well as salt marshes and sea grasses offer another major source of carbon removal and storage. When protected or restored these coastal ecosystems, which cover 490,000 km2 of the earth, can absorb and store huge amounts of what is referred to as ‘blue carbon’ – in fact, they have the ability to sequester carbon at a faster rate than other types of vegetation.

The regeneration of peatlands, a type of wetland including bogs and swamp forests, is also an important way of creating carbon sinks. Peatlands cover more than 3 million km2 around 3% of the world’s surface, and sequester 0.37 billion gigatonnes of CO2 per year.

What other types of solutions are there?

It’s difficult to predict CO2 levels that will remain in the UK economy. The National Grid’s 2020 Future Energy Scenarios (FES) Report, lays out a Steady Progress scenario in which decarbonisation is slow and limited to power and transport sectors. In this forecast there is still 258 million tonnes of CO2 being emitted in 2050.

Nature-based solutions’ ability to remove CO2 at such a scale can be limited by factors such as the land use needed, which can encroach on food crops for example. Nature based solutions are do not always offer permanent removal of CO2. Forest fires for example would release carbon stored in forests, damaging their ability to remove emissions.

Achieving the levels of carbon capture needed to reach net zero will require a variety of nature-based techniques and technologies are needed, all working in tandem to achieve a net zero future.

Man-made technologies include carbon capture methods such as bioenergy with carbon capture and storage (BECCS) and direct air carbon capture and storage (DACCS). But it can also include methods such as using wood or low-carbon concrete in construction There are more ambitious innovations at play too, such as stratospheric aerosols, cloud seeding, space mirrors, and painting surfaces with a reflective coating.

Fast facts

Go deeper

Button: What is bioenergy with carbon capture and storage (BECCS)?

Enviva Cottondale pellet plant catchment area analysis

18 August 2021

Sustainable bioenergy

The Enviva Cottondale pellet mill has a production capacity of 760,000 metric tonnes of wood pellets annually. Raw material used by the mill includes a combination of roundwood, chips, and secondary residuals (i.e., sawdust and shavings), with pine accounting for 80‐90% of total feedstock. In October 2018, Hurricane Michael passed through the centre of the Cottondale catchment area, causing significant damage to the forest resource with more than 500,000 hectares (ha) of forestland destroyed and an estimated loss of 42 million m3of timber (equivalent to around 4 times the UK annual production of roundwood).

This event has had an impact on the data trends for forest inventory, growth and harvesting removals – as harvesting levels were increased to salvage as much timber as possible before it became unusable due to decay. This can be clearly seen in many of the charts below. However, these forest areas have been restored and now continue to grow, allowing the catchment area to return to its pre-hurricane trends in the medium term.

Forest Area 

The catchment area around Enviva’s Cottondale pellet mill includes 4.3 million ha of land, based on the historical feedstock sourcing patterns of the mill. Timberland represents 68.7% (2.95 million ha) of the total land area in the Cottondale catchment area, this has increased slightly since 2000 from 67.8% and can be considered to have remained stable over this time period.  There are also around 300,000 ha of woodland (associated with agricultural land) and around 800,000 ha of cropland and pastureland.  Forestry is the dominant land use in this catchment area (Figure 1).

Figure 1: Land area by usage

Planted pine represents 33% of the timberland area, natural pine 20%, with 10% mixed stands and the remainder being hardwood forest of which 94% is naturally regenerated (Figure 2).  The breakdown of forest type and species composition has remained relatively stable and largely unchanged over the last 20 years, in contrast to other parts of the US South where some natural pine stands have been converted to planted pine. The pine and mixed forest areas are actively managed and produce the majority of the timber harvest in the catchment area. Despite the large area of hardwood forest, management and timber production is limited. Much of this area is classified as bottomland hardwood located alongside rivers, streams, and creeks and in streamside management zones (SMZs), which restricts active management. In addition, the proportion of this catchment area located in Florida contains a large area of swampland, which is largely composed of hardwoods and cannot be actively managed for timber production and is recognised as having important ecological value.

Figure 2: Breakdown of forest type

Volume and Growth

The overall trend of volume and growth in the Cottondale catchment area is of a maturing forest resource and an increasing accumulation of standing volume, particularly in the larger forest product classes (saw-timber and chip-n-saw). Figure 3 shows that total standing volume increased by 64 million m3 from 2000 to 2018, with the largest increases in the pine saw-timber and chip-n-saw categories. In 2018, the devastating impact of Hurricane Michael caused a substantial reduction in the standing volume across every product category with the total standing volume being reduced by 42 million m3. This event has had a significant impact on the forest resource and is a primary cause of recent data trends.

However, the overall long-term trend in the catchment area is of maturing forest and increasing inventory. This should continue in the long-term once the impact of the hurricane damage has been managed and replacement forest areas begin to mature.

Figure 3: Standing volume by product category

Pine pulpwood inventory increased steadily by around 8 million m3 from 2000 to 2013, reaching a peak of 49 million m3. This then declined slightly to 46 million m3 in 2018 due to the maturing age class of the forest and pulpwood forest growing into the larger size class of chip-n-saw and saw-timber forest (Figure 4), in addition to an increase in pulpwood demand as biomass markets became operational and ramped up production. Following the hurricane in 2018, the pine pulpwood inventory dropped by more than 10 million m3. 

Replanting and reforestation of damaged areas will ensure that future pine pulpwood production will increase again once these forests start to mature.

In the period from 2000 to 2018 pine sawtimber standing volume increased by 41.5 million m3 (78%) and chip-n-saw by 19.6 million m3 (73%), indicating a maturing age class and a growing forest resource. The 2018 hurricane caused a reduction in standing volume in both of these product categories of 11.6 and 8 million m3respectively (12% and 17% of the 2018 volume). However, the increasing trend is likely to continue once the forest area recovers.

Figure 4: Standing volume by product category

The growth drain ratio (GDR) is the comparison of average annual growth to removals (typically harvesting), where the growth exceeds removals the GDR will be in excess of 1 and this is considered sustainable, where removals exceed growth then the GDR will be less than 1 and this is not sustainable if maintained in the long-term – although in the short-term this can be a factor of large areas of mature forest with low growth rates and high rates of harvesting, short periods of high demand for a particular product or salvage harvesting after a natural disturbance. The GDR should be considered over a longer time period to ensure it reflects the long-term trend. In the period from 2003 to 2020 the combined GDR for pine products averaged 1.52 with a high of 1.84 and a low of 1.08 (Figure 5).

Figure 5: Growth to drain ratio by product category

The maturing forest resources can be clearly seen from the growth to removals data for each product category. Average tree sizes getting larger and more pulpwood class stands moving into the larger saw-timber and chip-n-saw categories. This trend can be seen by comparing the data values from 2003 and 2018 where saw-timber average annual growth increased by 90% (1.6 million m3), and removals by 41% (0.98 million m3).  Chip-n-saw growth increased by 73% (1.3 million m3) whilst removals increased by 160% (1.9 million m3). Pulpwood growth decreased by 7.5% (0.4 million m3) whilst removals increased by 63% (1.6 million m3).  Over this time period the total annual surplus of pine growth compared to removals averaged 3.7 million m3 per year (Figure 6).

Figure 6: Pine growth and removals by product category and year

Hardwood saw-timber and pulpwood removals declined by 20% and 40% respectively between 2000 and 2018, whilst growth increased by 23% for hardwood saw-timber and declined by 16% for hardwood pulpwood. The average annual hardwood surplus over this time period was 1.5 million m3 per year (Figure 7).

Figure 7: Hardwood growth and removals by product category and year

Despite a short-term imbalance in some product categories, the overall surplus of pine growth compared to removals has remained strong, with an average of 3.3 million m3 between 2000 and 2020, which includes the increased salvage harvesting in 2018 (Figure 8).

Figure 8: Cumulative annual surplus of growth compared to removals

Wood Prices

Stumpage price is the value paid to the forest owner for each category of product at the time of harvesting. The variation in prices in the Cottondale catchment area has been significant and shows some interesting trends. The higher value pine products (saw-timber and chip-n-saw) began with high stumpage values in 2000, as markets were strong for construction and furniture grade timber and supply limited at that stage due to the young age class and predominance of pulpwood stands at that time.  In 2008, following the global economic crisis and the crash in housing and construction markets, saw-timber prices declined substantially reaching a low of $23 per ton, a 47% decline from the 2000 price. This stumpage price has never recovered, despite an improvement in the economy and an increase in housing starts and demand for structural timber. The reason for the continued deflated saw-timber stumpage price is a substantial surplus of supply in this catchment area.  As the forest area has matured and more saw-timber grade stands are available, markets have been able to satisfy demand without an increase in price.

Pine pulpwood prices at Cottondale were lower than the US South-wide average in 2000 and remained relatively low until around 2013. A reduction in saw-timber production, and consequent reduction in mill residuals, due to the recession of 2008, led to a shortage of pulp mill feedstock and increased harvesting of pulpwood stands. This caused an increase in pine pulpwood stumpage values alongside an overall increase in demand as biomass and pellet markets began production around this time. The data shows a short-term spike in pine pulpwood stumpage prices in 2013-14, but this returned to a more normal trend as more saw-timber residues became available and pulpwood stumpage values have been around $10-11 per ton since 2015 (Figure 9).

Figure 9: Variation in stumpage value over time

Biomass demand 

Biomass demand in the Cottondale catchment area began in 2008 and has averaged around 800 thousand m3per year since that time with a high of just over 1 million m3 in 2013 to 2015 and a low of 200 thousand m3 in 2008. Other pulpwood markets have had an average annual demand of 3.97 million m3 between 2000 and 2020 with a high of 4.76 million m3 in 2018 and a low of 3.2 million m3 in 2009.  In 2020 the biomass market represented 16% of the total pulpwood demand in the Cottondale catchment area (Figure 10).

Figure 10: Total pulpwood demand

Forest Management

The average size of clear-cut harvesting sites from 2000 to 2020 has been 47 ha, ranging from 38 ha up to 56 ha. The average size of thinning sites has been 65 ha, ranging from 55 ha up to 76 ha. When isolating the period from 2000 to 2010 and 2011 to 2020, the averages and range remain very similar, suggesting that there has been no significant change in harvesting coupe size over this period.

Figure 11: Average size of harvesting sites

The impact of biomass and wood pellet demand on the key metrics in this catchment area are considered below. This is a summary of Hood Consulting’s view on the trends and impacts in the Cottondale catchment area.

Is there any evidence that bioenergy demand has caused the following:

Deforestation?

No. US Forest Service (USFS) data shows a 55,166-hectare (+1.9%) increase in the total area of timberland in the Enviva Cottondale catchment area since the Enviva Cottondale pellet mill commenced production in 2008. Furthermore, a strong positive relationship was identified between biomass demand and timberland area, suggesting that the increase in timberland area since 2008 can be linked, to a degree, to increased demand attributed to bioenergy.

A change in management practices (rotation lengths, thinnings, conversion from hardwood to pine)?

Inconclusive. Changes in management practices have occurred in the catchment area over the last two decades. However, the evidence is inconclusive as to whether increased demand attributed to bioenergy has caused or is responsible for these changes.

Clearcuts and thinnings are the two major types of harvests that occur in this region, both of which are long-standing, widely used methods of harvesting timber. TimberMart-South (TMS) data shows that thinnings accounted for 63% of total reported harvest area in the Cottondale market from 2005-2011 but only 39% of total harvest area reported from 2012-2020. Specifically, the decreased prevalence of thinning since 2012 can be linked to the strengthening of pine pulpwood markets and concurrent weakening of pine sawtimber markets beginning in the mid-2000s.

Prior to the bursting of the US housing bubble in 2006, timber management in this market had been driven to a large degree by pine sawtimber production. However, challenging market conditions saw pine sawtimber stumpages prices decline more than 40% from 2006-2011. At the same time, pine pulpwood markets started to strengthen, with pine pulpwood stumpage prices increasing more than 50% from 2006-2010. So, with sawtimber markets weakening and pulpwood markets strengthening, the data suggests that many landowners decided to alter their management approach (i.e. to take advantage of strong pulpwood markets) and focus on short pulpwood rotations that typically do not utilize thinnings.

Bioenergy has had an impact on this market by adding an average of roughly 680,000 metric tons of additional pine pulpwood demand to this catchment area annually since 2008. However, bioenergy has accounted for only 17% of total softwood pulpwood demand in this market since Enviva Cottondale’s startup. Ultimately, the shift in management approach that occurred in this market can be more closely linked to other factors, such as increased softwood pulpwood demand from non-bioenergy sources (i.e. pulp/paper) as well as the weakening of pine sawtimber markets.

Diversion from other markets?

No. Demand for softwood (pine) sawlogs increased an estimated 23% in the Cottondale catchment area from 2008-2020. Also, there is no evidence that increased demand from bioenergy has caused a diversion from other softwood pulpwood markets (i.e. pulp/paper), as softwood pulpwood demand not attributed to bioenergy has increased 25% since the Cottondale mill’s startup in 2008.

An unexpected or abnormal increase in wood prices?

Inconclusive. The startup of Enviva Cottondale added more than 900,000 metric tons of softwood pulpwood demand to the catchment area from 2008-2013, and this increase in demand coincided with a 28% increase in the delivered price of pine pulpwood (PPW) – the primary roundwood product consumed by the Enviva Cottondale mill. However, since 2013, delivered PPW prices have held flat, despite biomass-related softwood pulpwood demand falling to an average of roughly 635,000 tons per year since 2016, down more than 40% compared to 2013 peak levels. (Note the decrease in roundwood consumption was due to a higher utilization of secondary residuals). It’s also important to point out that the roughly 410,000-metric ton decrease in softwood biomass demand from 2013 to 2020 was offset by a roughly 455,000-metric ton increase in softwood pulpwood demand from other sources.

Statistical analysis did identify a positive relationship between softwood biomass demand and delivered PPW price. However, that relationship was found to be relatively weak. The relationship between delivered PPW price and softwood pulpwood demand from other sources was found to be much stronger, which was not unexpected to find given that softwood pulpwood demand not attributed to bioenergy has accounted for 83% of total softwood pulpwood demand in the catchment area since 2008.

Furthermore, there is some evidence linking the increase in pine sawmill chip prices to increased consumption of secondary pine residuals by Enviva Cottondale. Specifically, consumption of secondary pine residuals by Enviva Cottondale more than doubled from roughly 213,000 metric tons in 2012 to nearly 490,000 metric tons in 2016, and this increased consumption of pine residuals coincided with a nearly 20% increase in the price of pine sawmill chips. However, increased consumption of residuals by the bioenergy sector was only one of several contributing factors that can be linked to the increase in pine sawmill chip prices. Increased consumption of pine residuals by the pulp/paper industry also contributed to higher pine sawmill chip prices. In addition, there is a strong linkage between pine sawmill chip prices and softwood lumber production. Specifically, the increase in softwood lumber production that begun in the early-to-mid-2010s consequently resulted in the increased production of secondary residuals, and the increased availability of this lower-cost material led to greater competition and ultimately higher pine residual prices.

A reduction in growing stock timber?

No. From 2008 (the year Enviva Cottondale commenced production) up until Hurricane Michael struck in late-2018, total growing stock inventory increased an average of 1.8% per year (+19% total) in the Cottondale catchment area. Specifically, inventories of pine sawtimber and pine chip-n-saw increased 58% and 28%, respectively, while pine pulpwood (PPW) inventory decreased 4% over this same period.

However, note that the decrease in pine pulpwood inventory from 2008-2018 was not due to increased demand from bioenergy or increased harvesting above the sustainable yield capacity of the forest area, as annual growth of pine pulpwood exceeded annual removals every year throughout this period. Rather, this slight decrease in PPW inventory levels is more a reflection of the aging of the catchment area forest and the movement of stands classified as pulpwood to stands classified as chip-n-saw.

A reduction in the sequestration rate of carbon?

No. US Forest Service (USFS) data shows the average annual growth rate of total growing stock timber in the Cottondale catchment area decreased from 5.9% in 2008 to 5.2% in 2020, suggesting that the sequestration rate of carbon also declined slightly over this period. However, there is little evidence to suggest that increased demand attributed to bioenergy is responsible for this change.

The reduction in overall growth rate (and therefore reduction in the sequestration rate of carbon) is more a reflection of the aging of the catchment area forest. Specifically, growth rates decline as timber ages, and this is exactly what USFS data shows in the Cottondale catchment area, with the average age of growing stock timber increasing from less than 44 years of age in 2008 to nearly 46 years of age in 2020.

An increase in harvesting above the sustainable yield capacity of the forest area?

No. Growth-to-removals (G:R) ratios, which compare annual timber growth to annual timber removals, provides a measure of market demand relative to supply as well as a gauge of market sustainability. In 2020, the latest available, the G:R ratio for pine pulpwood (PPW), the predominant timber product utilized by the bioenergy sector, equaled 1.26 (recall that a value greater than 1.0 indicates sustainable harvest levels).

Note, however, that the PPW G:R ratio averaged 1.57 in the catchment area from 2013-2017 before falling to 1.20 in 2018 and averaging 1.27 since. This notable drop in 2018 was due to a nearly 35% increase in PPW removals (due to Hurricane Michael). It’s also important to note that while annual removals have moved back in line with pre-Michael levels since 2019, this lower PPW G:R ratio is likely reflective of the new norm (at least over the midterm). Hurricane Michael destroyed an estimated 22% of total pine pulpwood inventory in the Cottondale catchment area, and this loss in inventory will be reflected in reduced growth until the destroyed forests regenerate. However, in spite of this loss, adequate PPW inventory levels still remain and sustainable market conditions are expected to persist moving forward.

Timber growing stock inventory

Neutral. According to USFS data, inventories of pine pulpwood (PPW) decreased 25% in the catchment area from 2008-2020. However, this substantial decrease was due to Hurricane Michael, which destroyed nearly 520,000 hectares of catchment area timberland when it hit the Florida panhandle in late-2018. Prior to this event occurring, PPW inventory levels had held relatively steady, decreasing slightly but averaging 47.2 million m3 in the catchment area from 2008-2018. However, the destruction caused by Hurricane Michael resulted in the immediate loss of more than 10.3 million m3 of PPW inventory, or a 22% decrease compared to pre-hurricane levels.

Moreover, the slight decrease in PPW inventory levels that did occur from 2008-2018 was not due to increased demand from bioenergy. Typically, a reduction in inventory is linked to harvest levels above the sustainable yield capacity of the forest area, but in the Cottondale catchment area, annual growth of PPW exceeded annual removals every year throughout this period. Ultimately, the decrease in PPW inventory from 2008-2018 can be more closely linked to decreased pine sawtimber production beginning in the early to mid-2000s. Specifically, annual removals of pine sawtimber decreased 28% from 2003-2014, and the reduction in harvest levels over this period translated to a reduction in newly-re-established pine stands and ultimately the slight reduction in PPW inventory levels that occurred in the mid-to-late 2010s.

Timber growth rates

Neutral. Overall, timber growth rates declined slightly in the catchment area from 2008 (the year Enviva Cottondale commenced operations) through 2020. However, this decrease in timber growth rates was not due to increased demand attributed to bioenergy but rather to the aging of the catchment area forest. Specifically, USFS data shows the average age timber inventory in the Cottondale catchment area increased from an estimated 43.6 years of age in 2008 to 45.7 years of age in 2020.

Forest area

Positive. In the Enviva Cottondale catchment area, total forest area (i.e. timberland) increased more than 55,100 hectares (+1.9%) from 2008 through 2020, and this increase can be linked to several factors, including increases in softwood pulpwood demand (from both bioenergy and other sources) as well as conversion from farmland.

Specifically, the more than 55,100-hectare increase in catchment area timberland from 2008-2020 coincided with a 1.1-million metric ton increase in annual softwood pulpwood demand (roughly half of which was attributed to bioenergy). While statistical analysis identified moderately strong positive relationships between timberland area and both softwood biomass demand and non-bioenergy-related softwood pulpwood demand, a strong positive correlation was found between timberland and total softwood pulpwood demand – suggesting that the increases in timberland since 2008 can be attributed, in part, to the increase in total softwood pulpwood demand (from both bioenergy and other sources).

The more than 55,100-hectare increase timberland from 2008-2020 also coincided with a roughly 75,000-hectare decrease in farmland (i.e. cropland, woodland, and pastureland) over this period. Specifically, the catchment area experienced a roughly 31,800-hectare loss in cropland, 8,900-hectare loss in pastureland, and 34,300-hectare loss in woodland from 2008-2020. Furthermore, statistical analysis confirmed this inverse relationship, identifying a strong negative correlation between timberland and farmland in the Cottondale catchment area.

Wood prices

Negative / Positive. Total softwood pulpwood demand attributed to bioenergy in the Cottondale catchment area increased from zero tons in 2007 (the year prior to Enviva Cottondale’s startup) to over 1.0 million metric tons in 2013. Over this same period, the price of delivered pine pulpwood (PPW) – the predominant roundwood product utilized by Enviva Cottondale for wood pellet production – increased 42% (from $21.06 per ton in 2007 to $29.82 per ton in 2013).

However, the apparent link between increased softwood biomass demand and increased delivered PPW price is only loosely supported by statistical analysis, which identified a relatively weak positive relationship between these two variables. Furthermore, delivered PPW price has remained nearly unchanged in the catchment area since 2013, despite softwood biomass demand declining and averaging roughly 577,000 metric tons per year since 2016. (Note that the roughly 410,000-metric ton decrease in softwood biomass demand from 2013-2020 was offset by a roughly 455,000-metric ton increase in softwood pulpwood demand from other sources). Ultimately, the increase in delivered PPW prices in the catchment area can be linked to increased demand for softwood pulpwood from all sources, and roughly half of the 1.2-million metric ton increase in softwood pulpwood demand since 2007 can be attributed to bioenergy.

However, it’s also important to note that the increase in bioenergy-related wood demand has been a positive for forest landowners in the Enviva Cottondale catchment area. Not only has bioenergy provided an additional outlet for pulpwood in this market, but the increase in delivered PPW price resulting from increased softwood pulpwood demand from bioenergy has transferred through to landowners in the form of higher PPW stumpage prices. Specifically, over the six years prior to Enviva Cottondale’s startup, PPW stumpage price – the price paid to landowners – averaged roughly $7.40 per ton in the Cottondale catchment area. However, since 2010, PPW stumpage prices have averaged more than $11.15 per ton, representing a more than 50% increase compared to pre-mill startup levels.

Markets for solid wood products

Positive. In the Enviva Cottondale catchment area, demand for softwood sawlogs used to produce lumber and other solid wood products increased an estimated 23% from 2008-2020. This increase in softwood lumber production has consequentially resulted in an increase in sawmill residuals (i.e. chips, sawdust, and shavings) – by-products of the sawmilling process and materials utilized by Enviva Cottondale to produce wood pellets.

Specifically, softwood sawlog demand has increased more than 16% in the catchment area since 2014, and this increase in demand has coincided with a nearly 60% increase in pine residual purchases by Enviva Cottondale. (Note that pine residuals constituted 25% of total raw material purchases by Enviva Cottondale in 2014 but 41% of total raw material purchases in 2020). So, not only has Enviva Cottondale benefited from the greater availability of this sawmill by-product, but lumber producers have also benefited, as Enviva Cottondale has provided an additional outlet for these producers and their by-products.

Read the full report: Enviva Cottondale pellet plant catchment area analysis. 

This is part of a series of catchment area analyses around the forest biomass pellet plants supplying Drax Power Station with renewable fuel. Others in the series can be found here. 

What is bioenergy with carbon capture and storage (BECCS)?

18 May 2021

Carbon capture

What is bioenergy with carbon capture and storage (BECCS)? 

Bioenergy with carbon capture and storage (BECCS) is the process of capturing and permanently storing carbon dioxide (CO2) from biomass (organic matter) energy generation.

Why is BECCS important for decarbonisation? 

When sustainable bioenergy is paired with carbon capture and storage it becomes a source of negative emissions, as CO2 is permanently removed from the carbon cycle.

Experts believe that negative emissions technologies (NETs) are crucial to helping countries meet the long-term goals set out in the Paris Climate Agreement. As BECCS is the most scalable of these technologies this decade, it has a key role to play in combating climate change.

How is the bioenergy for BECCS generated?

Most bioenergy is produced by combusting biomass as a fuel in boilers or furnaces to produce high-pressure steam that drives electricity-generating turbines. Alternatively, bioenergy generation can use a wide range of organic materials, including crops specifically planted and grown for the purpose, as well as residues from agriculture, forestry and wood products industries. Energy-dense forms of biomass, such as compressed wood pellets, enable bioenergy to be generated on a much larger scale. Fuels like wood pellets can also be used as a substitute for coal in existing power stations.

How is the carbon captured?

BECCS uses a post-combustion carbon capture process, where solvents isolate CO2 from the flue gases produced when the biomass is combusted. The captured CO2 is pressurised and turned into a liquid-like substance so it can then be transported by pipeline.

How is the carbon stored?

Captured CO2 can be safely and permanently injected into naturally occurring porous rock formations, for example unused natural gas reservoirs, coal beds that can’t be mined, or saline aquifers (water permeable rocks saturated with salt water). This process is known as sequestration.

Over time, the sequestered CO2 may react with the minerals, locking it chemically into the surrounding rock through a process called mineral storage.

BECCS fast facts

Is BECCS sustainable?

 Bioenergy can be generated from a range of biomass sources ranging from agricultural by-products to forestry residues to organic municipal waste. During their lifetime plants absorb CO2 from the atmosphere, this balances out the CO2that is released when the biomass is combusted.

What’s crucial is that the biomass is sustainably sourced, be it from agriculture or forest waste. Responsibly managed sources of biomass are those which naturally regenerate or are replanted and regrown, where there’s a increase of carbon stored in the land and where the natural environment is protected from harm.

Biomass wood pellets used as bioenergy in the UK, for example, are only sustainable when the forests they are sourced from continue to grow. Sourcing decisions must be based on science and not adversely affect the long-term potential of forests to store and sequester carbon.

Biomass pellets can also create a sustainable market for forestry products, which serves to encourage reforestation and afforestation – leading to even more CO2 being absorbed from the atmosphere.

Go deeper:

  • The triple benefits for the environment and economy of deploying BECCS in the UK.
  • How BECCS can offer essential grid stability as the electricity system moves to low- and zero-carbon sources.
  • Producing biomass from sustainable forests is key to ensuring BECCS can deliver negative emissions.
  • 5 innovative projects where carbon capture is already underway around the world
  • 7 places on the path to negative emissions through BECCS

Evaluating regrowth post-harvest with accurate data and satellite imagery

13 May 2021

Sustainable bioenergy

  • Drax has been using effective post-harvest evaluations, which includes remote sensing technology and satellite imagery

  • Alongside sustainable forest management, monitoring can help support rapid regrowth after harvesting

  • Evidence shows healthy managed forests with no signs of deforestation or degradation

As part of Drax’s world-leading programme of demonstrating biomass sustainability, including ongoing work on catchment area analysis (CAA), responsible sourcing policy and healthy forest landscapes (HFL). We have also been trialling the use of high-resolution satellite imagery to monitor forest conditions on specific harvesting sites in the years after harvesting has taken place, in addition to the catchment area level monitoring of trends and data. Post-harvest evaluations (PHE) are an essential part of an ongoing sustainability monitoring process, ensuring that the future forest resource is protected and maintained and that landowners restore forests after harvesting to prevent deforestation or degradation.

The most effective form of PHE is for an experienced local forester to walk and survey the harvesting site to check that new trees are growing and that the health and quality of the young replacement forest is maintained.

Rapid regrowth

The images below show some of the sites surrounding Drax’s Amite Bioenergy pellet plant in Mississippi, with trees at various stages of regrowth in the years after harvesting.

A full site inspection can therefore enable a forester to determine whether the quantity and distribution of healthy trees is sufficient to make a productive forest, equivalent to the area that was harvested. It can also identify if there are any health problems, pest damage or management issues such as  weed growth or water-logging that should be resolved.

Typically, this will be the responsibility of the forest owner or their forest manager and is a regular part of ongoing forest management activity. This degree of survey and assessment is not practical or cost-effective where a third-party consumer of wood fibre purchases a small proportion (typically 20-25 tonnes per acre) of the low-grade fibre produced at a harvest as a one-off transaction for its wood pellet plant..  It is time consuming to walk every acre of restocked forest and it is not always possible to get an owner’s permission to access their land.

Forests from space

Therefore, an alternative methodology is required to make an assessment about the condition of forest lands that have been harvested to supply biomass, without the need to physically inspect each site.  One option is to use remote sensing and satellite imagery to view each harvested site in the years after biomass sourcing, this helps to monitor restocking and new tree growth.

Drax has been testing the remote sensing approach using Maxar’s commercial satellite imagery.  Maxar has four satellites on orbit that collect more than three million square kilometres of high-resolution imagery every day. Drax accesses this imagery through Maxar’s subscription service SecureWatch.

To test the viability of this methodology, Drax has been looking at harvesting sites in Mississippi that supplied biomass to the Amite Bioenergy pellet plant in 2015 and in 2017.  As part of the sustainability checks that are carried out prior to purchasing wood fibre, Drax collects information on each harvesting tract. This includes the location of the site, the type of harvest, the owner’s long-term management intentions and species and volume details.

This data can then be used at a later date to revisit the site and monitor the condition of the area. Third-party auditors, for instance Through Sustainable Biomass Program (SBP) certification, do visit harvesting sites, however this is typically during the year of harvest rather than after restocking. Maxar has historical imagery of this region from 2010, which is prior to any harvesting for wood pellets.  The image below shows a harvesting site near the pellet plant at Gloster, Mississippi, before any harvesting has taken place.

March 2010 (100m)

Satellite image © 2021 Maxar Technologies.

The image below shows the same site in 2017 immediately following harvesting.

December 2017 (100m)

Satellite image © 2021 Maxar Technologies.

If we look again at this same site three years after harvesting, we can see the rows of trees that have been planted and the quality of the regrowth. This series of images demonstrates that this harvested area has remained a forest, has not been subject to deforestation and that the regrowth appears to be healthy at this stage.

August 2020 (50m)

Satellite image © 2021 Maxar Technologies.

Another site in the Amite catchment area is shown below. The image shows a mature forest prior to harvesting, the site has been previously thinned as can be seen from the thinned rows that are evident in the imagery.

May 2010 (200m)

Satellite image © 2021 Maxar Technologies.

Looking at the same site in the year after harvesting, the clear cut area can be seen clearly. Some green vegetation cover can also be seen on the harvested area, but this is weed growth rather than replanted trees. Some areas of mature trees have been left at the time of harvesting, and are visible as a grey colour in the 2010 image. These are likely to be streamside management zones that have been left to maintain biodiversity and to protect water quality, with the grey winter colouring suggesting that they are hardwoods.

September 2018 (200m)

Satellite image © 2021 Maxar Technologies.

Three years after the harvest, in a zoomed in view from the previous image, clear rows of replanted trees can be seen in the imagery.  This demonstrates that the owner has successfully restocked the forest area and that the newly planted forest appears healthy and well established.

August 2020 (50m)

Satellite image © 2021 Maxar Technologies.

While examining different harvesting sites in satellite imagery, Drax noted that not every site had evidence of tree growth, particularly within the first three years after harvesting. Deliberate conversion of land to non-forest use, such as for conversion to pasture, agricultural crops or urban development, is likely to be evident fairly soon after harvesting.

Preparing for planting

Some forest owners like to leave a harvested site unplanted for a couple of years to allow ground vegetation and weed growth to establish, this can then be treated to ensure that trees can be planted and that the weed growth does not impede the establishment of the new forest, this process can mean that trees are not visible in satellite imagery for three to four years after harvesting.

The image below shows a site three years after harvesting with no evidence of tree growth.  Given that no conversion of land use is evident and that the site appears to be clear of weed growth, this is likely to be an example of where the owners have waited to clear the site of weeds prior to replanting.  This site can be monitored in future imagery from the Maxar satellites to ensure that forest regrowth does take place.

November 2020 (100m)

Satellite image © 2021 Maxar Technologies.

Drax will continue to use Maxar’s SecureWatch platform to monitor the regrowth of harvesting sites and will publish more detailed results and analysis when this process has been developed further.  The platform allows ongoing comparison of a site over time and could prove a more efficient method of analysis than ground survey.  In conjunction with the CAA and HFL work, PHE can add remote sensing as a valuable monitoring and evidence-gathering tool to demonstrate robust biomass sustainability standards and a positive environmental impact.

Go deeper: 

Discover the steps we take to ensure our wood pellet supply chain is better for our forests, our planet and our future here, how to plant more trees and better manage them, our responsible sourcing policy for biomass from sustainable forests and a guide to sustainable forest management of the Southern Working Forest.

Drax Biomass seeks stakeholder evaluation of wood procurement

23 March 2021

Sustainable bioenergy

Dear Stakeholder:

Drax Biomass Inc. (DBI) manufactures compressed wood pellets produced from sustainably managed working forests in the southern US.  Headquartered in Monroe, Louisiana, Drax Biomass owns and operates three existing wood pellet manufacturing plants: Amite Bioenergy in Gloster, Mississippi, Morehouse Bioenergy near Bastrop, Louisiana, and LaSalle Bioenergy near Urania, Louisiana.  Drax Biomass is also expanding to include three satellite sawmill operations in Arkansas (collectively referred to as Arkansas Bioenergy).  Pellets produced at Amite, Morehouse, and LaSalle are derived from low-grade roundwood, forest residuals, and sawmill residuals.  Pellets produced at the three satellites facilities will be derived purely from sawmill residuals.  Pellets are transported by train, truck, and barge, then loaded onto ships bound from Baton Rouge to the UK.  In the UK they are used at the Drax Power Station to generate flexible, renewable power for UK homes and businesses.  The use of sustainably sourced wood pellets is a part of Drax Group’s strategy to enable a zero-carbon economy and help the UK meet their climate change commitments.

To assure sustainable sourcing, DBI participates in four certification programs: FSC® Chain of Custody & Controlled Wood, SFI® Chain of Custody & Fiber Sourcing, the PEFC™ Chain of Custody and the Sustainable Biomass Program (SBP).  Underpinning DBI’s sustainability program is SBP’s Supply Base Evaluation which provides a formal framework for the evaluation of potential risks related to forest sourcing.  All plants share the same supply area and are considered under one Supply Base Evaluation.

This consultation serves two primary purposes (1) to attain SBP certification for the three Arkansas Bioenergy satellite plants (located in Leola, Russellville, and Bearden AR respectively), and to (2) expand the supply base for all plants to include three more counties in Oklahoma (Delaware, Adair and Cherokee).   We are specifically seeking input from stakeholders to test if risk evaluations and proposed mitigations remain reasonable for our supply base.  For those of you which received a consultation request in 2020 (for Amite and Morehouse recertification), you will find that there have been no changes made to our risk designations or risk mitigations.

You can find the Supply Base Evaluation document here.  Comments can be submitted via email during the period spanning March 23rdthrough April 23rd, 2021.

Thank you in advance for any feedback you can provide.

Sincerely,

Drax Biomass Team

What is a biomass wood pellet?

22 January 2021

Sustainable bioenergy

However, by compressing organic matter like wood, forest residues and sawdust into energy-dense pellets, biomass can be used for heating or renewable bioenergy generation at a much greater scale.

Why are pellets powerful?

The advantage of using biomass in the form of a pellet is its energy density. This refers to the amount of energy that can be stored in a given amount of a material.

On their own the wood and residues like wood chips and sawdust that make up biomass do not have a high energy density. A kilogram of wood, for example, stores little energy, compared to fuels like coal, diesel or uranium.

However, by compressing forest industry residues into a pellet, biomass becomes significantly more energy dense. Wood pellets can also have very low moisture content, giving them a high combustion efficiency – an important feature in power generation.

How are biomass pellets made?

Biomass pellets are made at a pelletisation plant. Here wood that is unsuitable for other industries like sawmill residues, are brought together.

The wood is chipped, screened for quality, heated to reduce its moisture content to below 12% and then converted into a fine powder. This is then pressed through a grate at high pressure to form the solid, short, dense biomass pellet.

How are pellets used in power generation?

Biomass pellets can be used to generate power in a similar way to coal, allowing existing coal power stations to be transformed to use renewable bioenergy instead.

A conveyor system takes pellets from storage through to pulverising mills, where they are crushed into a fine powder that is then blown into the power station’s boiler. Here the biomass is combusted as fuel, the heat from this combustion is used to make steam which powers the generators that produce electricity.

Biomass pellets’ density and uniform shape also makes them easier to transport and store in large quantities. However, it is essential that they are kept dry while in transit and that when stored in biomass domes the atmospheric conditions are carefully monitored and controlled to prevent unwanted combustion.

Biomass pellet facts

Are biomass pellets renewable? 

When forests are sustainably managed, and trees naturally regenerated or replanted and regrown in a human timeframe, it makes the biomass pellets sourced from them renewable.

It’s vital for the long-term energy generation that biomass pellets are sourced from responsibly managed forests and other industries that protect the environment and do not contribute to deforestation. Sourcing decisions must be science-based and not adversely affect the long-term potential of forests to store and sequester carbon.

Sustainable wood pellets are considered to be carbon neutral at the point of combustion. As they grow, forests absorb carbon from the atmosphere. When a biomass pellet is combusted, the same amount of atmospheric CO2 is released. The overall amount of CO2 in the atmosphere remains neutral, unlike with fossil fuels which release ancient carbon that has long fallen out of the natural carbon cycle.

Because sustainable bioenergy is low carbon when its lifecycle emissions, including supply chain CO2, are factored in, it is possible to turn it into a source of negative emissions, with the addition of carbon capture technology.

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What is renewable energy?

17 December 2020

Sustainable bioenergy

These differ to non-renewable energy sources such as coal, oil and natural gas, of which there is a finite amount available on Earth, meaning if used excessively they could eventually run out.

Renewable resources can provide energy for a variety of applications, including electricity generation, transportation and heating or cooling.

The difference between low-carbon, carbon neutral and renewable energy

Renewables such as wind, solar and hydropower are zero carbon sources of energy because they do not produce any carbon dioxide (CO2) when they generate power. Low-carbon sources might produce someCO2, but much less than fuels like coal.

Bioenergy that uses woody biomass from sustainably managed forests to generate electricity is carbon neutral because forests absorb CO2 from the atmosphere as they grow, meaning the amount of CO2 in the atmosphere remains level. Supply chains that bring bioenergy to power stations commonly use some fossil fuels in manufacturing and transportation. Therefore woody biomass is a low carbon fuel, when its whole lifecycle is considered.

Managing forests in a sustainable way that does not lead to deforestation allows bioenergy to serve as a renewable source of power. Responsible biomass sourcing also helps forests to absorb more carbon while displacing fossil fuel-based energy generation.

Nuclear is an example of a zero carbon source of electricity that is not renewable. It does not produce CO2,but it is dependent on uranium or plutonium, of which there is a finite amount available.

Managing forests in a sustainable way that does not lead to deforestation allows bioenergy to serve as a renewable source of power.

How much renewable energy is used around the world?

Humans have harnessed renewable energy for millions of years in the form of woody biomass to fuel fires, as well as wind to power ships and geothermal hot springs for bathing. Water wheels and windmills are other examples of humans utilising renewable resources, but since the industrial revolution fossil fuels, coal in particular, have been the main source of power.

However, as the effects of air pollution and CO2 produced from burning fossil fuels become increasingly apparent, renewable energy is gradually replacing sources which contribute to climate change.

In the year 2000 renewable energy accounted for 18% of global electricity generation, according to the IEA. By 2019, renewable sources made up 27% of the world’s electrical power.

Why renewable energy is essential to tackling climate change

The single biggest human contribution to climate change is greenhouse gas emissions, such as CO2, into the atmosphere. They create an insulating layer around the planet that causes temperatures on Earth to increase, making it less habitable.

Renewable sources of electricity can help to meet the world’s demand for power without contributing to global warming, unlike carbon-intensive fuels like coal, gas and oil.

Bioenergy can also be used to remove CO2 from the atmosphere while delivering renewable electricity through a process called bioenergy with carbon capture and storage (BECCS).

Forests absorb CO2 from the atmosphere, then when the biomass is used to generate electricity the same CO2 is captured and stored permanently underground – reducing the overall amount of CO2 in the atmosphere.

Humans have used renewable energy for millions for years, from wood for fires to wind powering boats to geothermal hot springs. 

What’s holding renewables back?

The world’s energy systems were built with fossil fuels in mind. This can make converting national grids difficult and installing new renewable energy sources expensive. However, as knowledge grows about how best to manufacture, build and operate renewable systems, the cost of deploying them at scale drops.

There are future changes needed. Renewables such as wind, solar and tidal power are known as intermittent renewables because they can’t generate electricity when there is no sun, wind or the tidal movement. For future energy systems to deliver enough power, large scale energy storage, as well as other flexible, reliable forms of generation will also be needed to meet demand and keep systems stable.

Renewable energy key facts:  

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