Agriculture as emission source and carbon sink : economic-ecological modelling for the EU-15

摘要

The thesis develops and applies analytical tools to describe economic and ecological impacts of greenhouse gas mitigation strategies in European agriculture. Agriculture is widely perceived as emission source, but actually it can also act as emission sink by sequestration of atmospheric carbon to agricultural soils. Thereby, soil carbon pools potentially store twice as much carbon as contained in the atmosphere. In view of this circumstance, the study analysed agricultural emission sources and mitigation scenarios in the area of conservation tillage and bio-energy production. The analysis was within a mixed-integer programming model optimizing total gross margins of typical farms of NUTS-II-regions in the EU-15. For this micro-economic analysis high quality region specific cost estimates for main agricultural products were indispensible. Thereby a new approach was developed that draws European accountancy data and German engineering cost data. The first dataset comprises of up-to-date crop-unspecific cost data as indicated by European bookkeeping farms. The second comprises of crop specific cost data from German farms. Through a combination of both datasets crop specific estimates of production costs on regional level for the EU-15 evolved. Another study that starts from accountancy data to deduct product cost estimates is currently funded by the European Commission (Farm Accountancy Cost Estimation and Policy Analysis of European Agriculture).By monetarizing greenhouse gas emissions, the Kyoto-Protocol has increased the demand for economic-ecological models to analyse emission scenarios. The study model, EU-EFEM, integrates biophysical data to site-specifically simulate soil carbon dynamics in terms of the mitigation scenario ?conservational tillage?. This approach provides a level of detail that is significantly superior to the one achieved by soil emission factors specified only to global climate zones, a few soil types, and soil management alternatives like provided by the global standard work for the calculation of greenhouse gas emissions, the guidelines of the Intergovernmental Panel on Climate Change (IPCC). The biophysical data was integrated from the EPIC-model to which an interface was established.In the analysis of the agricultural sink function increased input of organic matter, crop rotational modifications, and conservational tillage were assessed. A first scenario that could be monitored relatively easily forces minimum shares of conservational tillage per farm. It was shown that all farms in the EU-15 could comply even with a forced share of 100%. But on average, shares exceeding 80% entail economic losses, basically because of the incompatibility of certain current crop rotations with conservational tillage. Against the average loss of 20 ?/ha in case of 100% of forced conservational tillage, stand single farms facing a loss of 350 ?/ha. Simultaneously soil carbon accumulation remained at marginal levels. In another scenario that directly forces soil carbon accumulation while leaving the choice of the appropriate means to farmers, an accumulation of 181 million tCO2e was achieved. This value corresponds to a forced accumulation of 1.0 t C/ha, a rate out of reach for 25 out of all analysed NUTS-II-regions. Mitigation costs are at 70 ?/tCO2e in this case, but at 10 ?/tCO2e only if only those regions are considered in which the minimum accumulation rates can be achieved. The latter is a competitive value compared to current values of EU traded emission rights. Policy, however, should withdraw from a regulation forcing minimum SOC-accumulation. Main reasons are the difficult monitoring, which would be required on site level, and the absence of a success guarantee on side of farmers for taken measures. Designing effective political instruments, the humus balance as stipulated in the Cross-Compliance regulation of the reformed AGENDA 2000 represents a prefect starting point.The study also analyzed agricultural biogas production with electricity recovery in a combined heat and power (CHP) unit and different (waste) heat utilization rates. European agriculture could increase annual profits by 1.6 to 9.2 billion ? depending mainly on waste heat utilization rate. In the best case, the contribution to climate change mitigation is 263 Mill tCO2e while realising a mitigation gain of 5 ?/tCO2e when excluding subsidies comprised in the feed-in tariff.Being an issue in any discussion about agricultural bio-energy production, the study also analyses the competition for agricultural land with food and feed production. Tapping the full agricultural biogas production potential, 28.7% of grassland and 18.5% of arable land would be bound, although the study constrains biogas production to co-fermentation with manure. The impacts of this competition on agricultural prices could not be analysed in this study, since the applied model is a farm model and not a market equilibrium model. By means of literature research, however, it was concluded that subsidies of biogas production should focus on promoting the fermentation of manure and the utilization of waste heat in order to limit area competition and not to promote the utilization of cultivated biomass.