Modelresultaten maatregelen en maatregelpakketten voor reductie van broeikasgasemissies op Nederlandse melkveebedrijven

This study is part of a project to reduce greenhouse gas (GHG) emissions from milk production (Public-Private Partnership ‘Low Carbon Dairy’). This study analysed the effectiveness and costs of individual measures and a package of measures, as well as potential trade-offs with other sustainability indicators. For this purpose, model calculations were made for three farm types, based on Dutch dairy farms. These farm types were: extensive on peat, medium intensive on clay, and intensive on sand. Six measures to reduce GHG emissions were calculated for these farms: 1) feeding brewer’s grains as a substitute for concentrates; 2) applying grass-clover without artificial fertiliser on 25% of the grassland area; 3) increasing milk production by 500 kg per cow; 4) feeding a methane-inhibiting feed additive 3-NOP; 5) reducing the carbon footprint of concentrates; and 6) applying daily removal of slurry in combination with mono-digestion. The grass-clover measure was not applied on peatland; and mono-digester was applied only on the intensive farm. Due to the large reduction in GHG emissions relative to cost, the measures methane-inhibiting feed additive (3-NOP) and manure digestion were relatively cheap measures per tonne of GHG emission reduction. Increasing milk production had a positive economic effect in addition to lower GHG emissions. In practice, this measure is probably less easy to apply and may be more expensive with higher manure disposal prices. Replacing concentrates with brewer’s grains or concentrates with a low carbon footprint led to a greater reduction and better cost-effectiveness on the more intensive farms, because in the initial situation, relatively many high-protein concentrates with a high footprint were fed there. Greater savings were possible on these. Applying grass-clover turned out to be relatively expensive in the calculations. This result strongly depends on the crop yield of grass-clover compared to grassland. Few studies are available to estimate the crop yield of grass-clover. Also, results differ between these studies and between years within studies. More field studies are therefore needed for a good estimate. Measures were calculated separately and as a total package. Feeding brewer’s grains, applying grass-clover and increasing milk production also affected other aspects, such as buying or selling feed and manure disposal. Implementation of the measure package reduced GHG emissions by 124 to 285 g CO2 eq/kg fat- and protein-adjusted milk (FPCM). The largest reduction was achieved in the intensive farm type, partly because the measure manure digester was applied only on that farm type. This measure resulted in the largest reduction in GHG emissions (-103 g CO2 eq/kg FPCM). After this measure, feeding a methane-inhibiting feed additive had the largest effect on all farm types (-66 to -94 g CO2 eq/kg FPCM). Trade-offs from measures on other sustainability characteristics, namely ammonia emissions from fertilisation and grazing and from barn and storage, N soil surplus, and protein from own land, were limited. The total economic impact of the packages of measures was negative for all farms, ranging from around -€12,000 to almost -€34,000 per farm per year. Per 100 kg of milk, this was -€1.65 to -€2.09. No allowance for measures or premiums for lower greenhouse gas emissions per kg of milk have been taken into account in the calculations. Overall, the measure packages resulted in GHG emission reductions of 10% to 31% compared to the baseline. With more far-reaching measures, e.g., by replacing a larger share of concentrated feed with by-products or feeding higher concentrations of feed additives, or also applying mono-digestion on the extensive and medium-intensive farm, larger reductions can be realised. To what extent these maximum measure packages come close to the 50% GHG emission reduction target will be investigated within this project. A more general comment on this study is that the model used calculates normatively, using good agricultural practice as a basis. In practice, quite large differences in GHG emissions occur on comparable farms. Analyses based on practical data from dairy farms that perform better on sustainability show that, on average, these farms also perform better economically. This means that it is important to first look at the baseline situation and whether optimisation can be achieved regardless of additional measures.