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Size matters: scaling principles for the prediction of the ecological footprint of biofuels

Periodic Reporting for period 4 - SIZE (Size matters: scaling principles for the prediction of the ecological footprint of biofuels)

Reporting period: 2020-03-01 to 2020-08-31

To address energy security and climate-change concerns, fossil-based fuels and materials are to be replaced. Biofuels and biomaterials are considered important candidates, but controversial at the same time due to large uncertainties concerning the claimed environmental benefits. The goal is to develop and apply a sound, analytical framework for assessing global biodiversity impacts of habitat destruction and greenhouse gas emissions caused by biofuel production. We showed that biofuel production with carbon capture and storage can indeed physically result in substantial climate mitigation, more than the current emission levels of CO2, but at the same time result in large land requirements. For a time horizon of 30 years the benefits of climate mitigation for biodiversity are expected to be smaller than the impacts of land use change. For a 80 year time horizon, the benefits and impacts are more balanced. It appears to be extremely important to use land as long as possible for feedstock production and carefully select locations with low biodiversity impacts and not only use the carbon sequestration potential as a selection criterium.
GHG EMISSIONS FROM BIO-ENERGY
Global climate change mitigation potential of bioenergy with carbon capture and storage
We quantified in a spatially-explicit assessment the life-cycle GHG emissions for lignocellulosic crop-based bioenergy with carbon capture and storage (BECCS) at the global scale. Our results indicate that over a period of 30 years, BECCS can only play a modest role. Over the full century, however, BECCS the physical potential is 40 Gt of CO2 sequestered per year – more than the current total annual emissions. On the other hand, full global implementation of BECCS could lead to competition with other land uses. In the most extreme scenario, up to 2.4 billion hectares of land would be required by 2100 to grow lignocellulosic crops for BECCS, which equals 16 % of the total land surface area on Earth. Overall, our findings suggest that policymakers ought to complement BECCS with other options for GHG emission reduction and carbon dioxide removal. The work was published in Nature Climate Change and will be used to update the integrated assessment model IMAGE with climate mitigation options.

Biomass residues as 21st century bioenergy feedstock
In the 21st century, modern bioenergy could become one of the largest sources of energy, partially replacing fossil fuels and contributing to climate change mitigation. Agricultural and forestry biomass residues form an inexpensive bioenergy feedstock with low greenhouse gas (GHG) emissions, if harvested sustainably. We analysed quantities of biomass residues supplied for energy and their sensitivities in various climate change mitigation scenarios across eight integrated assessment models (IAMs), and compared them to literature-estimated residue availability. IAM results vary substantially, at global and regional scales, but indicate that residues could meet over 50% of bioenergy demand towards 2050, and up to 30% towards 2100. Higher bioenergy demand or biomass prices increase the quantity of residues supplied for energy, though their effects level off as residues become depleted. GHG emission pricing and land protection can increase the costs of using land for bioenergy crop cultivation, which increases residue use at the expense of bioenergy crops. In most IAMs and scenarios, supplied residues in 2050 are within literature-estimated residue availability, but outliers and sustainability concerns warrant further exploration. We conclude that residues can cost-competitively play a large role in the 21st century bioenergy supply, though uncertainties remain concerning (regional) forestry and agricultural production and resulting residue supply potentials. The work was used as input in the latest IPCC assessment.


BIODIVERSITY IMPACTS FROM BIO-ENERGY

Influence of climate change on biome distributions
We performed a global assessment of the potential impacts of climate change on the extent of global biomes, using a trait-based modelling approach. We showed that tropical biomes are likely to flourish under future climate change, while tundra will be affected most, decreasing by 30% of its current extent and up to 48% under extreme climate change. We projected that at least 70% of temperate forest and grassland, and 50% of boreal forest would shift all moving northward. Overall our analysis addresses the need for a robust and thorough assessment of the potential impact of climate change on biome extent.

Using land cover time series to assess species extinction risk
Habitat loss and degradation are probably the main responsible of biodiversity decline. The increasing demand for cropland products such as biofuel, is one of the main drivers of habitat conversion. Here we used from land cover change time series between 1992 and 2015 to derive a number of parameters to estimate the conservation status of species of 9,948 bird and 4,898 mammal species under the IUCN Red List framework. We then applied the IUCN guidelines to assess the Red List category for each species using these estimates. We predict around 481 species to be more threatened than currently assessed, and around 118 of Data Deficient species to be at risk of extinction. Our work will be considered to more regularly update the IUCN Red Lists of vertebrate species.

Biodiversity losses and gains of Bioenergy with Carbon Capture and Storage (BECCS)
We analysed the implications of BECCS on both impacts of land-use change (LUC) compared to benefits of mitigated climate change. LUC impacts are determined using global-equivalent, species-area relationships, while the positive effect of mitigated climate change on biodiversity is based on meta-analysis information. We found that global vertebrate species extinctions from LUC per unit of negative emissions achieved (0.055-7.7 species lost/Gtonne CO2 sequestered) are uncertain, but lower with i) longer lifetimes of BECCS systems, ii) less overall deployment of crop-based BECCS, and iii) optimal land allocation (i.e. prioritise locations with lowest species loss per negative emission potential). Tentative comparison shows that LUC effects most likely outweigh climate mitigation effects over 30 a year period, but that this trade-off is less clear over 80 years.
1. We quantified GHG emissions of bio-energy life cycles with and without carbon capture and storage at the global scale in a geospatially-explicit way.

2. We projected the current and future ecosystem impacts from habitat alternation and climate change caused by global bio-energy production.