A new report published this month in the academic journal Annual Review of Resource Economics once again underscores the environmental credentials of replacing fossil fuels with wood biomass. The meta-analysis, compiled by researchers Md Farhad H. Masum and Puneet Dwivedi from the University of Georgia’s Warnell School of Forestry and Natural Resources and Kamalakanta Sahoo from the US Forest Service, adds additional strength to recommendations from the European Union, the United Kingdom, and the UN Intergovernmental Panel on Climate Change that countries use wood biomass as part of their strategies to replace coal, meet their carbon emission reduction targets, and mitigate global climate change.
The report represents a comprehensive review of existing studies, analyzing the trajectory of wood-based bioenergy in the United States, and the environmental costs and benefits of wood biomass. Most notably, the report looked at two areas that biomass opponents have often cited – how wood biomass sourcing affects forest size, and how wood biomass compares with fossil fuels in terms of carbon emissions.
The report finds that on both counts, wood biomass is a win for forests and carbon reduction.
Wood Biomass Strengthens Forests
The report confirms what landowners have long been saying on the ground – that without the incentives of the wood biomass industry, more land would be converted to other uses, such as development. The report notes that:
Projections show that in the absence of additional demand for wood pellets, natural timberland area is projected to decline by 450–15,000 km2 by 2030, mainly through urbanization and pine plantation establishment. In contrast, under the high wood pellet demand scenario, more (2,000–7,500 km2) natural timberland area is retained and more (8,000–20,000 km2) pine plantation is established.
What Masum, Sahoo and Dwivedi note here is that the absence of demand for wood biomass would actually result in deforestation up to 15,000 square kilometers (5,791 square miles), roughly the size of the entire state of Connecticut. That is a massive potential loss in forest area due to increased urbanization. Conversely, increased demand for wood pellets retains thousands more square kilometers in natural timberland area.
Wood Biomass Would Reduce Carbon Emissions Compared To Fossil Fuels in the US
The report also notes that studies find that wood-based electricity reduces carbon emissions by between 77% and 99% compared to fossil fuels, and has “considerably lower” carbon intensity than coal-based electricity in the US.
Based on various forest management choices and biomass processing methods, the carbon intensity of wood-based electricity can range from 12 to 47 gCO2e/MJ (Figure 6). These estimates are considerably lower than the carbon intensity (324 gCO2e/MJ) of coal-based electricity in the United States (EIA 2018a). Huang & Bagdon (2018) reported lower greenhouse gases (12.2 gCO2e/MJ) because they have considered the direct combustion of mixed biomass from ponderosa pine to produce electricity. They compared coal-fired and biomass-based power production for several air pollutants and found that wood-based electricity saves about 95% of carbon emissions. Fan et al. (2011) compared pyrolysis oil from poplar, forest residue, sawmill residue, and willow biomass under three scenarios of replacing coal, natural gas, and oil for electricity production. They reported a 77% to 99% carbon savings for power generation compared to its fossil fuel alternative. Among them, carbon savings were highest when pyrolysis oil replaces coal and lowest when it replaces natural gas. The carbon intensity of electricity derived from sawmill residue was lowest (23–29 gCO2e/MJ), whereas the electricity derived from forest residues was most carbon intense (37–47 gCO2e/MJ). Burning chips from intensively managed slash pine emitted 21–25 gCO2e/MJ of electricity (Dwivedi & Khanna 2014a) based on the choice of biomass—logging residue, pulpwood, or combined. These estimates suggest high carbon savings in the biopower sector compared to fossil fuel. Other studies also reported significantly lower carbon emissions for electricity generation from cofiring biomass compared to coal (Mann & Spath 2001, Robinson et al. 2003, Heller et al. 2004, McKechnie et al. 2011, Loeffler & Anderson 2014, Sebastián et al. 2011).
Wood Biomass Reduces Carbon Emissions Compared To Fossil Fuels Abroad
The report also examined the carbon intensity of biopower from wood pellets shipped abroad. Wood pellets are increasingly being used to replace coal-generated electricity in retrofitted power plants across Europe. Masum, Sahoo and Dwivedi again find that studies show that wood pellets reduce carbon emissions compared to fossil fuels, even when shipped across the Atlantic in the form of wood pellets.
Pelletization increases the carbon intensity of electricity derived from wood pellets. Estimates of carbon intensity electricity derived from wood pellets range from 37 and 82 gCO2e/MJ based on forest management systems and transportation distances (Figure 7). Even after adding carbon emission (155 kg CO2e/metric ton of wood) from pelletization (Dwivedi et al. 2011), the carbon intensity of electricity derived from the wood pellets relative to coal-based electricity is lower by at least 75% in the United States. Dwivedi et al. (2011) estimated and compared the global warming impact of electricity production from slash pine produced and used in Florida and the Netherlands. They concluded that electricity from wood pellets has a lower global warming impact than their fossil fuel counterparts in both places and, obviously, it is significantly lower in Florida. This study reports a net savings of between 49% and 72% for every unit of electricity produced using imported wood pellets instead of fossil fuel in the Netherlands. These savings are even higher in Florida, between 74% and 84%. The authors recommended that tightening the energy efficiency standards in the supply chain could further reduce the carbon intensity of electricity generated from wood pellets.
This latest meta-analysis adds further weight to the recommendations of the United Nations that countries embrace wood bioenergy as a key tool to mitigate global climate change.