Assessment of the state of the art of technologies for the processing of digestate residue from anaerobic digesters

Abstract

Anaerobic digestion is widely used as an important source of renewable energy. With the increasing number and capacity of biogas plants also, adequate treatment technologies for whole digestate - the residue from anaerobic digestion - are gaining attention. In this study the state of the art of digestate processing is analysed, and currently used treatment schemes and the various technological processes involved are evaluated. The study combines data and experiences from existing large-scale digestate processing facilities in Austria, Germany, Switzerland and Italy, as well as know-how from technology providers and relevant research projects. However, the field of digestate processing is still quite new and little detailed information about the performance of different technologies at industrial scale is available. Digestate processing is gaining importance since digestate utilisation can become an important bottleneck when increasing biogas production. In addition, the production of renewable fertiliser from digestate is increasingly of interest to replace fossil fertilisers. This study is the first profound attempt to establish an assessment of the state-of-the-art technologies in use.

Avaliação do Desempenho Ambiental do Aproveitamento do Biogás em Fecularias de Mandioca no Estado do Paraná

“…Esse processo de consumo do material orgânico por bactérias anaeróbias resulta no biogás e nos restos digeridos (sem odor). Os resíduos digeridos podem ser utilizados na agricultura como fertilizantes, devido ao elevado conteúdo de nutrientes (FUCHS;DROSG, 2013). Essa tecnologia também vem sendo adotada na gestão de resíduos em aterros sanitários e tratamento de águas residuais (STARR et al, 2012).…”

Recovery of nutrients from biogas digestate with biochar and clinoptilolite

“…The most common practice of utilising the liquid fraction of digestate is direct field application if the biogas plant is in the vicinity (Drosg et al, 2015). However, direct application of digestate may raise practical and environmental problems if the biogas plant is farther away (Fuchs & Drosg, 2013). Therefore, processes to concentrate nutrients have been proposed aiming not only to treat the liquid fraction of digestate to overcome the problems related to direct application, but also to recover of nutrients of which natural reserves are being depleted such as phosphorus and potassium.…”

“…Separated solids can directly be applied due to lower transportation costs and decreased storage volume than liquid digestate (Teglia et al, 2011a;Fuchs & Drosg, 2013). On the other hand, separated solids can be further stabilised through composting to be used as a soil amendment (Teglia et al, 2011b) or can be thermally dried (Pantelopoulos et al, 2016).…”

“…However, ion exchange is only marginally applied in practice, usually for final ammonium removal after membrane processes (Drosg et al, 2015). Some researchers studied removal of ammonium and phosphorus from treated pig production and pre-treated dairy wastewaters by ion exchange (Sánchez et al, 1995;Milan et al, 1997;Henriksen et al, 1998;Nguyen & Tanner, 1998) removal process after membrane separation or evaporation (Guo et al, 2007;Fuchs & Drosg, 2013). However, none of these studies reported ion exchange from digestate or the liquid fraction, which has a much higher ammonium concentration compared to treated pig production and dairy wastewaters.…”

“…Digestate from the anaerobic digestion of manure and other organic wastes has a nutrient content which typically is favorable for use as a crop fertiliser, with direct land application often being the most cost-effective solution (Rico et al, 2011;Fuchs & Drosg, 2013). However, digestate is not an easy by-product to handle due to its high water content and consequently its large volume and low nutrient concentration.…”