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Whether the use of industrial wood pellets for bioenergy is part of the problem of climate change or part of the solution to climate change has been heavily debated in the academic and political arena. The uncertainty around this topic is impeded by contradicting scientific assessments of carbon impacts of wood pellet use. Spatially explicit quantification of the potential carbon impacts of increased industrial wood pellet demand, including both indirect market and land-use change effects, is required to understand potential negative impacts on carbon stored in the landscape. Studies that meet these requirements are scarce. This study assesses the impact of increased wood pellet demand on carbon stocks in the landscape in the Southern US spatially explicitly and includes the effects of demand for other wood products and land-use types. The analysis is based on IPCC calculations and highly detailed survey-based biomass data for different forest types. We compare a trend of increased wood pellet demand between 2010 and 2030 with a stable trend in wood pellet demand after 2010, thereby quantifying the impact of increased wood pellet demand on carbon stocks in the landscape. This study shows that modest increases in wood pellets demand (from 0.5 Mt in 2010 to 12.1 Mt in 2030), compared to a scenario without increase in wood pellet demand (stable demand at 0.5 Mt), may result in carbon stock gains of 103–229 Mt in the landscape in the Southern US. These carbon stock increases occur due to a reduction in natural forest loss and an increase in pine plantation area compared to a stable-demand scenario. Projected carbon impacts of changes in wood pellet demand were smaller than carbon effects of trends in the timber market. We introduce a new methodological framework to include both indirect market and land-use change effects into carbon calculations in the landscape. • Whether wood pellets are reducing or exacerbating climate change is heavily debated. • This spatially explicit study includes indirect effects of markets and land-use. • A modest increase in wood pellet demand result in carbon stock gains of 103–229 Mt. • Carbon gains are due to pine plantation expansion and natural forest conservation. [ABSTRACT FROM AUTHOR]

This study assessed the feasibility of mobilising maize and wheat residues for large-scale bioenergy applications in South Africa by establishing sustainable residue removal rates and cost of supply based on different production regions. A key objective was to refine the methodology for estimating crop residue harvesting for bioenergy use, while maintaining soil productivity and avoiding displacement of competing residue uses. At current conditions, the sustainable bioenergy potential from maize and wheat residues was estimated to be about 104 PJ. There is potential to increase the amount of crop residues to 238 PJ through measures such as no till cultivation and adopting improved cropping systems. These estimates were based on minimum residues requirements of 2 t ha −1 for soil erosion control and additional residue amounts to maintain 2% SOC level. At the farm gate, crop residues cost between 0.9 and 1.7 $ GJ −1 . About 96% of these residues are available below 1.5 $ GJ −1 . In the improved scenario, up to 85% of the biomass is below 1.3 $ GJ −1 . For biomass deliveries at the conversion plant, about 36% is below 5 $ GJ −1 while in the optimised scenario, about 87% is delivered below 5$ GJ −1 . Co-firing residues with coal results in lower cost of electricity compared to other renewables and significant GHG (CO 2 eq) emissions reduction (up to 0.72 tons MWh −1 ). Establishing sustainable crop residue supply systems in South Africa could start by utilising the existing agricultural infrastructure to secure supply and develop a functional market. It would then be necessary to incentivise improvements across the value chain. [ABSTRACT FROM AUTHOR]