Life cycle modelling of environmental impacts of application of processed organic municipal solid waste on agricultural land (Easewaste)

Abstract

A model capable of quantifying the potential environmental impacts of agricultural application of composted or anaerobically digested source-separated organic municipal solid waste (MSW) is presented. In addition to the direct impacts, the model accounts for savings by avoiding the production and use of commercial fertilizers. The model is part of a larger model, Environmental Assessment of Solid Waste Systems and Technology (EASEWASTE), developed as a decisionsupport model, focusing on assessment of alternative waste management options. The environmental impacts of the land application of processed organic waste are quantified by emission coefficients referring to the composition of the processed waste and related to specific crop rotation as well as soil type. The model contains several default parameters based on literature data, field experiments and modelling by the agro-ecosystem model, Daisy. All data can be modified by the user allowing application of the model to other situations. A case study including four scenarios was performed to illustrate the use of the model. One tonne of nitrogen in composted and anaerobically digested MSW was applied as fertilizer to loamy and sandy soil at a plant farm in western Denmark. Application of the processed organic waste mainly affected the environmental impact categories global warming (0.4-0.7 PE), acidification (-0.06 (saving)-1.6 PE), nutrient enrichment (-1.0 (saving)-3.1 PE), and toxicity. The main contributors to these categories were nitrous oxide formation (global warming), ammonia volatilization (acidification and nutrient enrichment), nitrate losses (nutrient enrichment and groundwater contamination), and heavy metal input to soil (toxicity potentials). The local agricultural conditions as well as the composition of the processed MSW showed large influence on the environmental impacts. A range of benefits, mainly related to improved soil quality from long-term application of the processed organic waste, could not be generally quantified with respect to the chosen life cycle assessment impact categories and were therefore not included in the model. These effects should be considered in conjunction with the results of the life cycle assessment.

Material Resources, Energy, and Nutrient Recovery from Waste: Are Waste Refineries the Solution for the Future?

“…a substitution rate of 20%. The substitution of P and K was assumed 100% (that is, all P and K applied substituted corresponding amount of mineral fertilizers) conformingly with the approach of (60). This is in accordance with similar studies (e.g.…”

“…The distribution of N into NH 3 , NO 3 -, and organic N was set to 13%, 0.2%, and 86.8% conformingly with (60). The air emission of NH 3 and N 2 O were assumed to 0.21% (i.e., 1.6% of the NH 4 + content of the compost) and 1.5%, respectively, of the N applied conformingly with (60,62). The emission of NO 3 -to water bodies was set to 20% of the applied N according to the findings of (62).…”

Greenhouse gas emissions from conventional and organic cropping systems in Spain. II. Fruit tree orchards

“…The effect is higher than our estimate at 20 years but lower at 100 years, as a result of the assumption of carbon content stabilization in the 20-100-year period in IPCC methodology. This assumption contrasts with modeling studies that predict that carbon will continue changing, even if at a lower rate, during the whole 100-year period (Hansen et al 2006;Powlson et al 2008; AlvaroFuentes and Paustian 2011).…”

“…The resulting net soil carbon exchange is shown in Table 1. In the impact assessment, the model was adjusted to 100 years by considering that average C sequestration rate in the 0-100-year period was 50 % of that in the initial 0-20-year period, based on the average change in published longterm modeling studies (Hansen et al 2006;Powlson et al 2008; Alvaro-Fuentes and Paustian 2011). …”

Anaerobic digestion and digestate use: accounting of greenhouse gases and global warming contribution

“…The digestate will to some extent substitute the use of inorganic fertilizer depending on the availability and amount of nutrients. The present paper follows Hansen et al (2006) in assuming that the farmer will act rationally and comply with national legislation when using digestate as fertilizer substitution.…”