Abstract
Crop rotations are part of current agricultural practice, since they and their effects can contribute to a sustainable agricultural cropping system. However, in current Life Cycle Assessment (LCA) studies, crop rotation effects are insufficiently considered, since these effects are difficult to measure. LCA studies from crop production typically take only one vegetation period into account. As a result, the consideration of how the assessed crop is influenced by the previous crop (crop rotation effects) including: (1) nutrient carryover, (2) reduction in operational requirements and (3) different intensity and timing of farming activities, is outside of the system boundary. However, ignoring these effects may lead to incorrect interpretation of LCA results and consequently to poor agricultural management as well as poor policy decisions. A new LCA tool called the “Model for integrative Life Cycle Assessment in Agriculture (MiLA)” is presented in this work. MiLA has been developed to assess GHG emissions and cumulative energy demands (CED) of cropping systems by taking the characteristics of crop cultivation in rotation into account. This tool enables the user to analyze cropping systems at farm level in order to identify GHG mitigation options and energy-efficient cropping systems. The tool was applied to a case study, including two crop rotations in two different regions in Germany with the goal of demonstrating the effectiveness of this tool on LCA results. Results show that including crop rotation effects can influence the GHG emission result of the individual crop by −34% up to +99% and the CED by −16 up to +89%. Expanding the system boundary by taking the whole crop rotation into account as well as providing the results based on different functional units improves LCA of energy crop production and helps those making the assessment to draw a more realistic picture of the interactions between crops while increasing the reliability of the LCA results.
Highlights
The use of biomass for energy production has been promoted as an environmentally friendly and energy-efficient way for heat, electricity and fuel production compared to fossil fuels
Agriculture including energy crops (EC) production is a highly complex system influenced by farm-specific factors such as pedoclimatic conditions and crop management
Expanding the system boundary by taking the entire CR into account as well as providing the results based on different functional units improves Life Cycle Assessment (LCA) accounting for EC production and supports the assessment of energy-efficient cropping systems and the development of greenhouse gas (GHG) reduction plans at farm level
Summary
The use of biomass for energy production has been promoted as an environmentally friendly and energy-efficient way for heat, electricity and fuel production compared to fossil fuels It is assumed, that the well-considered expansion of bioenergy production can improve the sustainability of energy generation by reducing greenhouse gas (GHG) emissions and by helping to secure energy supply (European Commission, 2009). Increased maize-based biomethane production has caused a specialization in maize in short rotations, up to the point of monocultures (Koçar and Civaş, 2013) These practices result in less diversified crop rotation (CR, the sequence of crops grown on the same field), which in turn can generate potential environmental problems such as soil damage through soil erosion or soil compaction, or an increased risk of nutrient leaching (European Environment Agency, 2007). EC-specific characteristics regarding, e.g. crop nutrient contents and biogas generation potential were analyzed in the EVA project, and the datasets derived from this were integrated in MiLA
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