Environmental accounting of closed-loop maize production scenarios: Manure as fertilizer and inclusion of catch crops

Abstract

The agri-food sector has moved towards a more linear production economy, partly caused by worldwide food demand. One clear example is the intensification of livestock production, with consequent manure-management and feed-production challenges, the effects of which have led to large environmental problems. Currently, efforts are being made to move the agricultural sector towards closed-loop alternatives. To ensure high environmental performance of these alternatives, realistic quantification of environmental impacts is needed. Thus, using Life Cycle Assessment (LCA) tools, we analyzed the environmental profile of six closed-loop maize scenarios focusing on different combinations of mineral fertilizer, digested organic fertilizer (digestate) from a manure co-digestion biogas plant, and rotation with (or without) catch crops (CCs) as a strategy to prevent nitrate leaching to groundwater and as a co-substrate in the biogas plant.Results demonstrated that replacing a large portion of the mineral fertilizers with digestate could help offset much of the total potential impact of global warming (by 25-35 %), resource depletion (by 94-96%), photochemical ozone formation (by 17-22 %), ozone depletion (by 96-99%) or even avoid it entirely as in freshwater eutrophication. However, digestate production and application contributed greatly to acidification (51%) and particulate matter (51-52%) categories, with minor differences depending on the species of CC used. An optimal combination of both digestate and mineral fertilizers is recommended. The incorporation of CCs in a maize rotation can reduce freshwater eutrophication impacts but increase global warming potential. Conclusions were drawn suggesting better management strategies to decrease environmental impacts of maize production.

Alternative Management Systems of Beef Cattle Manure for Reducing Nitrogen Loadings: A Case-Study Approach

“…In China, the proportion of livestock manure used in biogas production increased rapidly from 2005–2010, benefiting from biogas project’s national promotion [ 45 ]. An extensive literature has focused on the cost–benefit analysis or feasibility analysis of manure management strategies, including AD, mostly using the life-cycle assessment for individual farms [ 46 , 47 ]. Despite the high upfront costs of biogas produced by AD, it could be a profitable strategy given subsidies and tax credits for renewable energy projects [ 14 , 48 ].…”

Performance and environmental accounting of nutrient cycling models to estimate nitrogen emissions in agriculture and their sensitivity in life cycle assessment

“…The impacts were calculated for 1 t of harvested maize dry matter (DM) (Table 9). Importantly, the variation in the values was caused only by the fertilizer emissions, since the ones related to machinery, fuels and other emissions were maintained the same as in Montemayor et al (2019).…”

“…The estimated emissions were inventoried in SimaPro software v. 8.5 (Pré Consultants 2017) using a scenario provided by Montemayor et al (2019). The impacts were characterized using the ILCD 2011 midpoint method to verify how variations in emissions estimations influence LCA impact results.…”

“…The impacts were characterized in the Simapro software (Pré Consultants 2017), using a scenario provided by Montemayor et al (2019) and the models' emission estimates (Table 8). The impact categories analysed with the ILCD 2011 midpoint method were 'Climate change (CC)', 'Particulate Matter (PM)', 'Photochemical Ozone Formation (POF)', 'Acidification (AC)', 'Terrestrial Eutrophication (TE)' and 'Marine Eutrophication (ME)'.…”

“…It is important to highlight that only Animo takes into account the fertilizer application practices (e.g. broad sprayer, hose, injection), illustrating a limitation in the other models since many studies have found that practices can influence NH 3 volatilization (Bittman et al 2014;Søgaard et al 2002;Brentrup et al 2000; with an example of its site-specific application and use in Montemayor et al 2019 Denitrification is the process by which NO − 3 is reduced to N 2 in a total reduction or NO 2 and N 2 O in a partial reduction. In PEF, total denitrification producing N 2 is assumed using the EF 0.09 kg N 2 /kg N applied.…”