Abstract
Biogas is an alternative source of energy for fossil fuels. In the process of transforming organic materials into biogas significant amounts of valuable digestate are produced. In order to make the whole process sustainable digestate should be utilized this is a constraining factor in the development of the biogas industry. Consequently, there is an on-going search for new technologies to process digestate, allowing to broaden the range of possible ways of digestate utilization. One of such possibilities is technology of nitrogen (N) and phosphorus (P) recovery from the anaerobic digestate. In this study results of physicochemical analysis of materials flowing through the farm-scale bio-refinery producing struvite (STR) and ammonium sulphate (AS) are presented. Struvite was precipitated from the liquid fraction of digestate (LFDS). Ammonia was bound by sulphuric acid resulting in obtaining ammonium sulphate. The STR obtained was of medium purity and contained other macronutrients and micronutrients that further enhanced its agronomic value. The P recovery effectiveness, counted as the difference between the Ptot content in the material before and after STR precipitation was 43.8%. The AS was characterized by relatively low Ntot and Stot content. The Ntot recovery efficiency reached 43.2%. The study showed that struvite precipitation and ammonia stripping technologies can be used for processing digestate however, the processes efficiency should be improved.
Highlights
The progressing concentration of animal production causes a growing problem of environmental pollution
The total content of studied macronutrients was similar in raw (S) and digestated slurry (DS)
The contribution of water-soluble nutrients in total forms was higher in the liquid fraction of digestate (LFDS) (Table 1)
Summary
The progressing concentration of animal production causes a growing problem of environmental pollution. The problem is so serious that in some European countries systemic solutions began to be introduced forcing farmers to implement technologies aimed at the export of nitrogen and phosphorus (P) from farms [1]. This is exemplified by Dutch agriculture [2]. Due to a large excess of phosphorus occurring in farms with intensive livestock production, the Dutch government introduced legislation to limit the amount of phosphate used in agriculture. Farmers are eligible for state-founded payments when they exported phosphorus from their farm. Proper allocation of nitrogen (N) and P from manure between areas with excess of the components and those where their deficits are supplemented with mineral fertilizers will provide measurable
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