Implementation of GHG mitigation on intensive dairy farms: Farmers' preferences and variation in cost effectiveness

Abstract

The need for mitigation of greenhouse gas (GHG) emissions from dairy farms has been widely acknowledged. However, there is barely any knowledge on GHG emissions and mitigation options on commercial dairy farms. Most of the farmers are not aware of the GHG emissions on their farms and their attitude towards suggested mitigation measures is largely unknown. This study aims to provide insight in the variation of GHG emissions on commercial dairy farms and in the farmers' preferences for mitigation options and to investigate the effects of these options on GHG emissions and farm economy. The average GHG emission on the commercial farms was 1.08 kg CO 2 -equivalents per kg milk. The variation in emissions could be attributed to a combination of factors as soil type, fertilizer input, grazing system and feeding management. The preferred mitigation options were an increase of the milk production per cow, replacement of concentrates with single by-products, the use of more maize in animal feeding, the use of a heat pump and heat re-use from milk and reduction of the fertilizer N input. Farmers tend to choose mitigation options that are relatively simple and either cost effective or with only relatively small additional costs. The most promising mitigation options with respect to cost effectiveness are less replacement of dairy cattle and replacement of concentrates by single by-products grown in the vicinity of the farm. Other mitigation options which lead to land use change might be less effective due to possible trade offs. Overall, a total mitigation of 310 to 360 g CO 2 -equivalents per kg milk is achievable. This is a reduction of 25 to 30% compared to 1990. It is expected that this reduction can be achieved with relatively little costs. Keywords Mitigation Nitrous oxide Methane Greenhouse gases Farm economics Abatement costs 1 Introduction Livestock production is a significant source of greenhouse gas (GHG) emissions, its contribution has been estimated at 18%, based on a food chain approach ( Steinfeld et al., 2006 ). Therefore their figure is higher than the IPCC approach of total agriculture, which is about 14% ( IPCC, 2007 ). In The Netherlands, the contribution of agriculture, following the IPCC approach, is calculated at 9%, of which the dairy sector is a significant contributor. E.g. 50% of the national total of nitrous oxide (N 2 O) and methane (CH 4 ) emissions comes from livestock ( Van der Maas et al., 2009 ). Over the past decades, research has focused on quantifying emissions and on defining emission factors for N 2 O, CH 4 and carbon dioxide (CO 2 ). An important result is the tiered set emission factors of the IPCC Guidelines ( IPCC, 2006 ). Emission factors have been incorporated in a wide range of models to calculate emissions from agriculture. The models range from field level ( Vuichard et al., 2007 ), via farm level ( Schils et al., 2005; 2007a; Del Prado and Scholefield, 2008 ) to regional level ( Velthof et al., 2009 ). The need for mitigation of emissions has been acknowledged widely and also in The Netherlands mitigation policy has been defined by the government ( VROM, 2007 ). Many mitigation options have been defined in the last years ( Smith et al., 2008 ). Reducing N 2 O losses have been categorized ( Oenema et al., 2001 ) increasing the nitrogen use efficiency and reducing the N 2 O emissions per kg of N output. This can be realized by optimizing methods and timing of N application, reducing fertilizer inputs, using ammonium based fertilizers, using nitrification inhibitors, improving drainage, preventing soil compaction and reducing grazing time. Reduction of CH 4 emissions can be realized by increasing the maize fraction of rations ( Beauchemin et al., 2008 ), using starch and additives ( Shibata and Terada, 2010 ) and by manure digestion ( Amon et al., 2007 ). Improving milk production per cow and reducing the number of young stock reduce emissions of both CH 4 and N 2 O ( Schils et al., 2005 ). CO 2 emissions can be reduced by changing grassland renovation or no renovation at all ( Davies et al., 2001; Mori and Hojito, 2007 ); increasing the area of permanent grassland, reduced energy use and other energy sources in farm and field activities ( Smith et al., 2008 ). It has been emphasized that due to the many interactions in a livestock system, trade offs can occur. For instance, reduced grazing time will reduce N 2 O emissions, but this can partly be offset by more CH 4 due to changes in the animals' ration and more CO 2 due to a higher energy use ( Schils et al., 2005 ). As mitigation measures ultimately have to be implemented by farmers themselves, farm models can be used to define successful mitigation options. Schils et al. (2005; 2007b) have defined a number of possible mitigation options and paid special attention to cost effectiveness. Calculations were carried out for a limited number of experimental farms and intensively coached pilot farms, as well as for non existing average farms. However, there is barely any knowledge on GHG emissions and mitigation options on commercial dairy farms. Most of the farmers are not aware of the GHG emissions on their farms and their attitude towards suggested mitigation measures is largely unknown. To increase the farmers' awareness of GHG emissions extension projects were initiated on commercial dairy farms in The Netherlands. Farmers selected one or more mitigation options for implementation on their farm. For a selection of these farms the baseline GHG emissions and the effect of the preferred mitigation options were calculated with a farm simulation model. The collected data provide insight in the range of GHG emissions on commercial farms, and in the farmers' preferences for mitigation options. Furthermore, the study provided information on the variation in cost effectiveness of the selected mitigation options due to differences in farm structure. This study aims to provide insight in the variation of GHG...