GELUC: Greenhouse gas effects of global land-use competition

The world population is expected to grow to nine billions in the next decades. In combination with economic growth, this may result in a 70-100% increase of agricultural demand until 2050. Motivated by concerns over the finiteness and adverse climatic effects of fossil fuels, efforts are undertaken to raise the supply of biomass for bioenergy and raw materials. Studies such as the Global Energy Assessment, the IPCC Special Report on Renewable Energy (SRREN) and the 5th Assessment Report of the IPCC suggest that biomass use for those purposes will increase by a factor of 2-5 until 2050. Increases in biomass demand may drive up pressures on terrestrial ecosystems, contribute to greenhouse gas (GHG) emissions and result in an extension of land use into unused areas as well as in an intensification of land use in other areas. Systemic effects related to increasing land-use compe- tition drive such trends but are at present scarcely understood. The project GELUC aims to develop the consistent, data-based model BioBaM-GHG (Biomass Balance Model with Greenhouse Gas Emissions). BioBaM-GHG will link biomass flows consistently with spatially explicit land-use data and assess the biophysical option space of developments of, e.g., diets, bioenergy, food-chain losses, yields, livestock feed conversion ratios and land use. Based on emission factors from LCA databases and IIASAs GAINS model it will establish comprehensive GHG accounts for feasible scenarios, separately for 11 world regions in 2050 and including trade flows and associated emissions. BioBaM- GHG will rely on a substantial extension and further development of the BioBaM model by a consistent and comprehensive GHG emission module. It will be able to transparently capture GHG effects related to systemic feedbacks in the global land system. Because BioBaM-GHG does not use optimization algorithms but assesses the biophysical (im)possibility of combinations of future changes in key system parameters, it can comprehensively assess option spaces under controlled framework conditions and provide their full GHG emission account. Options to be analysed include the area demand effects of a promotion of organic agriculture and of bioenergy, changes in area demand and GHG emissions that may result from switches in diets or reduced food-supply-chain losses. The GHG costs of increasing yields (e.g. due to higher inputs of fertilizers) can be compared to GHG benefits of reduced area demand. GHG emissions of trade-related transport will be consistently integrated in the calculations. GELUC closes an important gap in the current understanding of systemic effects in the global land system. It will contribute to advancements of science in land-system research, in the analysis of socioeconomic metabolism as well as in the analysis of biogeochemical effects of increased production and use of bioenergy (also biomass coupled with carbon capture and storage, or BECCS) and highlight options to reduce GHG emissions in the global land-use system.

The world population will grow to 9-10 billion until 2050. Together with projected economic growth, this implies that demand for agricultural products could rise by 70 -100% over the level of the year 2000. The environmental effects of fossil fuels (e.g., climate heating) and their finite nature motivate efforts to replace them by renewable resources such as biomass. The use of biomass for energy and raw materials could hence rise by factors 2 -5 in the next decades. Rising biomass demand may imply the use of so far unused lands, as well as a more intensive use of already used lands. This is expected to result in considerable emissions of greenhouse gases (GHG). Systemic effects resulting from increasing land-use competition could play a big role in that respect. Within GELUC, the diagnostic biophysical model Bio BaM-GHG was developed to enable researchers to assess such effects. Diagnostic means that the model performs neither dynamic simulations nor (economic) optimizations, e.g. according to cost - benefit criteria. Biophysical means that the model includes only biophysical parameters such as the land area used for defined purposes, the yields achieved on that land and biomass - conversion processes from production to consumption, in particular livestock feeding. The model also calculates GHG emissions from these processes, including the relevant systemic interactions (e.g., reforestation, changes in land-use intensity). BioBaM-GHG (Biomass Balance Model with Greenhouse Gas Emissions) is capable of consistently linking spatially explicit data on land use with biomass flow data. It performs comprehensive GHG calculations for large numbers of possible future scenarios. Systemic interactions in the global land system are assessed by calculating large numbers of scenarios and analyzing the results across the entire option space. The model was developed in close collaboration with IIASA researchers working with the GAINS model, in particular in terms of nitrogen flows. Based on research in GELUC, 25 articles in peer-review journals were published, and a large number of additional outputs was generated. Project results underline the importance of systemic effects in the global land system for future GHG emissions, in particular with reference to biomass -based products such as bioenergy. The general assumption that biomass burning for energy is C- neutral vis-à-vis the atmosphere is shown to be invalid: systemic effects imply that leveraging higher bioenergy potentials will drive up emissions per unit of bioenergy. Future changes in human food consumption as well as livestock feeding emerge as key drivers of future GHG emissions from the food system, whereas future crop yields are shown to be of lesser importance. While higher yields may reduce land demand (at any given level of supply), they also enable adoption of more wasteful consumption practices. Moreover, GHG emissions for additional fertilizers required to produce higher yields are also significant.