Dr Jeanette Whitaker, Knowledge Exchange Fellow, discusses some of the issues raised in a new GCB Bioenergy paper on bioenergy and land-use change
Optimal use of land is one of the global challenges of our generation as we attempt to derive a wide range of services from the land (food, feed, fibre, fuel, etc.) while also protecting biodiversity and preventing further environmental degradation. At the same time, mitigation of climate change requires a wide range of reduction measures to be deployed globally if we are to keep warming below 2°C.
The UK government's recently launched 'Clean Growth Strategy' describes an important role for sustainable biomass in contributing to the UK’s low carbon future. To deliver this strategy, policymakers will need a robust evidence base to assess the most cost-effective and sustainable options for bioenergy deployment.
Environmental benefits and risks of bioenergy crops
Perennial bioenergy crops have significant potential to mitigate climate change by reducing greenhouse gas (GHG) emissions from energy generation, yet large-scale cultivation of these crops also presents environmental risks. Over the last decade, significant progress has been made in understanding the environmental benefits and risks of this transition to perennial bioenergy crops, addressing concerns that land-use change could result in increased rather than decreased GHG emissions. However, synthesis of these studies was needed to support evidence-based decision-making by governments.
In 2015, a workshop of international researchers, policymakers and industry representatives was convened at the Centre for Ecology & Hydrology in Lancaster to discuss bioenergy and land-use change. In our recent paper in GCB Bioenergy (published October 2017) we discuss six statements formulated during the workshop which summarise current understanding of the environmental costs and benefits of land-use change to perennial bioenergy crops, in the context of the whole life-cycle of bioenergy production.
One-metre deep sampling to assess soil carbon stocks in bioenergy crops (Photo: Rebecca Rowe)
Greenhouse gas savings from bioenergy
Our analysis indicates that perennial bioenergy crops can deliver significant climate mitigation, with maximum GHG savings achieved where crops are grown on soils with low carbon stocks and conservative nutrient application, accruing additional environmental benefits such as improved water quality. There are environmental risks associated with increasing land-use change and not all bioenergy production pathways will deliver the GHG savings targeted in renewable energy policies but a strong and increasingly comprehensive evidence base is now available to support the development of a sustainable bioenergy industry.
"...a strong and increasingly comprehensive evidence base is now available to support the development of a sustainable bioenergy industry."
It is critical for the future momentum of the bioenergy industry that the key areas of scientific consensus and our ability to quantify uncertainties on bioenergy carbon savings are clearly communicated, if we are to meaningfully support and engage in developing policies for sustainable bioenergy deployment which can contribute to the global goal of mitigating climate change.
Six statements framing the consensus of opinion, remaining uncertainties and challenges for perennial bioenergy crops and land-use change:
- N2O emissions from perennial crops strongly depend on the previous land-use with the greatest risk of large emissions during crop establishment
- Planting perennial bioenergy crops on low carbon soil will minimise soil carbon losses in the short-term and promote soil carbon sequestration in the long-term
- Variability in soil carbon stock changes influences the lifecycle GHG balance of bioenergy production much more than variability in nitrogen-related emissions over most common assessment timescales
- Perennial bioenergy crops can provide substantial climate mitigation when used to replace fossil fuels but land-use tensions must be mitigated
- Perennial bioenergy crops marginally reduce water availability at landscape scale but improve water quality through reduced nitrate leaching
- Ecosystem process-based models are essential for assessing bioenergy viability and environmental performance at landscape and regional scales, but they have only recently been applied to evaluate specific land-use policies and strategies
Full paper reference:
Whitaker J, Field J L, Bernacchi C J, Cerri C E P, Ceulemans R, Davies C A, DeLucia E H, Donnison I S, McCalmont J P, Paustian K, Rowe R L, Smith P, Thornley P and McNamara N P (2017). Consensus, uncertainties and challenges for perennial bioenergy crops and land-use change. GCB Bioenergy, online early (open access). DOI: 10.1111/gcbb.12488
Watch Jeanette's lecture on the Local to Global Challenges of Bioenergy and Land Use: