Integrated life cycle assessment of biotreatment and agricultural use of domestic organic residues : Environmental benefits, trade-offs, and impacts on soil application

Extensive agricultural activities have been shown to degrade soils, promoting research into improving soil quality. One such method is to increase the amount of organic matter in the soil, and domestic organic residues (DOR) are commonly used for this purpose. The environmental impact of DOR-derived products, from production to agricultural application, remains unclear in current research. With the aim to have a more comprehensive understanding of the challenges and opportunities in DOR management and reuse, this study extended the boundaries of Life Cycle Assessment (LCA) to include the transport, treatment, and application of treated DOR on a national level while also quantifying soil carbon sequestration that has been less addressed in relevant LCA studies. This study focuses on The Netherlands, where incineration predominates, as a representative case to explore the benefits and trade-offs of moving towards more biotreatment for DOR. Two main biotreatments were considered, composting and anaerobic digestion. The results indicate that biotreatment of kitchen and yard residues generally has higher environmental impacts than incineration, including increased global warming and fine particulate matter formation. However, biotreatment of sewage sludge has lower environmental impacts than incineration. Substitution of nitrogen and phosphorus fertilisers with compost reduces mineral and fossil resource scarcity. In fossil-based energy systems like The Netherlands, replacing incineration with anaerobic digestion yields the highest benefit for fossil resource scarcity (61.93 %) due to energy recovery from biogas and the predominant use of fossil resources in the Dutch energy system. These findings indicate that replacing incineration with biotreatment of DOR may not benefit all impact categories in LCA. The environmental performance of substituted products can significantly influence the environmental benefits of increased biotreatment. Future studies or implementation of increased biotreatment should consider trade-offs and local context.