Anaerobic digestate production is expected to rise sharply—from 31 to 177 million tonnes (dry matter) by 2050—yet its direct application to fields is restricted by EU nitrate regulations. Given its high nitrogen, phosphorus, and potassium content, new sustainable methods are being explored to recover nutrients and produce bio-fertilizers. This study evaluated several membrane-based filtration sequences and found ultrafiltration to be the most effective step, enabling higher nutrient concentrations in the reverse-osmosis product and improved water recovery. The ultrafiltration concentrate also proved to be a suitable, and even faster-acting, inoculum for biogas production compared to conventional digestate. These findings highlight practical options for both nutrient recovery and enhanced biogas system performance.
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