University of Twente Student Theses


Green energy generation and sustainable farming: pollution reduction potential of manure digesters on Dutch dairy farms

Reijers, Niek (2021) Green energy generation and sustainable farming: pollution reduction potential of manure digesters on Dutch dairy farms.

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Abstract:Due to human activities, global warming is seriously increasing the earth's temperature. Keeping the temperature rise within the limits of 1.5 degrees Celsius is currently the global ambition (IPCC, 2018; IEA, 2020). The achieve this ambition significant reductions of greenhouse gas (GHG) emissions caused by human activities are required. According to the Intergovernmental Panel of Climate Change (IPCC) the reduction of carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) are specifically required (IPCC, 2018). The production and conversion of fossil energy resources are considered to be among the major causes of the global temperature rise. In the Netherlands, next to the production, conversion and consumption of fossil energy resources, the intensity of dairy production is considered a major contributor to methane and nitrogen dioxide emissions (European Commission, 2020; Ritchie and Roser, 2020). According to official Dutch statistics, the Dutch dairy sector is causing about 46% of the nitrogen (N) emissions in the Netherlands (Adviescollege Stikstofproblematiek, 2020; Environmental Data Compendium, 2019). These emissions are the downside of the high global production standards and economic relevance of Dutch dairy farming. Against this background, our research focused on the question; if and to what extent digestion of manure reduces emissions in Dutch dairy farming. Manure digestion addresses several current societal challenges. It contributes to the availability of green energy, it is assumed to reduce GHG and N emissions and provides perspectives for sustaining intensive livestock farming in the Netherlands. To date researching this combination of societal challenges is rarely done. It is the major theme of our research, which was guided by the following research question: what is the scale of GHG and nitrogen pollutants emissions reduction and net renewable energy generation when implementing manure digesters on Dutch dairy farms? By tradition, manure is used as natural fertiliser on farmland. Currently, manure digestion is practised only on a small number of the 16,000 Dutch dairy farms despite the production of 47 million tons of manure annually. Thus, there is a huge potential for manure mono-digestion. To analyse the biogas generation and emission reduction potential of farm-based manure digestion, we developed a new farm-scale model to assess the benefits of manure digestion in terms of biogas yield and GHG and N-pollutant emission reduction. The model is based on a farm-based manure life-cycle with two management options: traditional manure storage and manure digestion for biogas production. The model has been developed and designed in close cooperation with farmers in the province of Overijssel and realistically integrated all variables relevant in the farm-based manure life-cycle. Moreover, the model used real-life data for analysing the differences in both manure management scenarios in terms of GHG emissions (N2O, CH4, CO2) and the N-pollutants (NH3 and NOX). Data of four different farms has been used in the analysis. This data has been obtained from the KringloopWijzer, which is a common data format used by all dairy farms in the Netherlands (van Dijk et al., 2020). The model has integrated several well-established emissions methodologies which have been adapted to work at a farm scale. Among others we used the air pollutant emission inventory guidebook 2019 by EMEP/EEA (Amon et al., 2019; Garcia et al., 2019), the Guidelines for National Greenhouse Gas inventories by IPPC (Dong et al., 2006) and the Dutch National Emissions Model for Agriculture (Lagerwerf et al., 2019; van Bruggen et al., 2020). By running the model we compared the emissions between the traditional manure storage scenario and the scenario with farm-scale manure digestion. The results of the four different dairy farms show that at least 29% of the total-N emissions can be reduced by introducing manure digestion on a dairy farm in the Netherlands. If the barn is of the lowest emission housing type, the emission reduction can increase to about 44%. Compared to the traditional manure storage scenario, manure digestion reduces the methane (CH4) emissions by 80%. Due to the sustainable energy generation capabilities of manure digester, the net carbon dioxide (CO2) emissions of dairy farms also significantly reduce and in some cases more than completely offset. The total GHG emission reduction of these four farms expressed in CO2-eq. is 1.24 million kg CO2. These results indicate the diverse benefits of manure digestion in terms of GHG and N-pollutant emissions reduction and green energy production. Our analysis also indicates that a nationwide introduction of farm-based manure digestion could significantly reduce emissions by removing 19.3 million kg N as well as 62.8 million kg of CH4 and at the same time generating 1.51 TWh of sustainable energy, avoiding 562.1 million kg CO2. The combined reduction of GHG, expressed in CO2-eq., through the introduction of manure digesters in the Netherlands is 3,268.23 million kg CO2. Our model is easily accessible as an Excel tool to facilitate farmers and policy makers as a decision support tool for estimating emission reduction potential at the farm. Future research could add a financial module to the tool for assessing the financial feasibility of investments in manure digestion technology at the farm.
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Programme:Civil Engineering and Management MSc (60026)
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