Integrated manure management to reduce environmental impact: II. Environmental impact assessment of strategies

•New strategies for integrated pig and dairy cattle manure management were assessed.•LCA was used to calculate the environmental impact and nitrogen use efficiency.•Environmental impact was reduced by at least 65% under North West EU practice.•Nitrogen use efficiency was more than doubled and P2O5 over application reduced.•Newly designed strategies avoid pollution swapping and reduce environmental impact.

Manure management contributes to adverse environmental impacts through losses of nitrogen (N), phosphorus, and carbon (C). In this study, we aimed to assess the potential of newly designed strategies for integrated manure management (IS) to reduce environmental impact. An important aspect of the strategies was that they prevented pollution swapping. Life cycle assessment was used to compute climate change (CC), fossil fuel depletion (FFD), terrestrial acidification (TA), marine eutrophication (ME), particulate matter formation (PMF), N use efficiency (NUE), and phosphorus over application rate (POA), relative to the crop demand for N. We applied the IS to North West European practice (Ref) and included the Dutch current situation of progressive manure management (NL) to illustrate the potential of the IS to reduce environmental impact. Manure management in Ref included production and management of liquid and solid dairy cattle manure applied to maize and grass, and liquid pig manure applied to wheat. A Monte Carlo uncertainty simulation was done to assess the effect of variation in N and C losses and N uptake by crops on the comparison with Ref, IS, and NL. Results showed that the IS reduced all environmental impacts in all manure product and crop combinations and more than doubled the NUE (70% compared with maximum 33% in Ref). Main causes were: segregation of pig and dairy cattle urine and feces inside the housing system reduced methane (CH4) and ammonia (NH3) emissions; addition of zeolite to solid dairy cattle manure reduced NH3 emission; sealed storages in all IS reduced volatilization of N and C; bio-energy production from the feces reduced the production of fossil electricity and heat; and finally N emissions in the field were reduced by ammonia emission reducing application techniques and improved application management (tillage, field traffic en synchronization of manure product application with crop demand). Compared with the Ref, NL had lower TA, PMF, POA, and higher NUE, except for solid cattle manure applied to grass. This result indicates that the Dutch regulations to reduce NH3 emissions were successful, but that CC can be improved. Compared with NW EU practice, IS reduced environmental impact up to 185% for CC, up to > 700% for FFD, up to 96% for TA, up to 99% for ME, up to 100% for PMF, up to 110% for POA and more than doubled the NUE. We concluded that the designed IS avoid pollution swapping in the entire manure management system.