Co-digestion of manure with grass silage and pulp and paper mill sludge using nutrient additions

A Review of the Chemistry of Anaerobic Digestion: Methods of Accelerating and Optimizing Process Efficiency

The anaerobic digestion technology has been in existence for centuries and its underlying theory established for decades. It is considered a useful technology for the generation of renewable energy, and provides means to alleviate problems associated with low access to energy. However, a great deal of current research is targeted towards the optimization of this technology under diverse digestion process conditions. This review presents an in-depth analysis of the chemistry of anaerobic digestion and discusses how process chemistry can be used to optimize system performance through identification of methods that can accelerate syntrophic interactions of different microorganisms for improved methanogenic reactions. Recent advances in addition to old research are discussed in order to offer a general but comprehensive synopsis of accumulated knowledge in the theory of anaerobic digestion, as well as an overview of previous research and future directions and opportunities of the AD technology. Achieving a sustainable energy system requires comprehensive reforms in not just economic, social and policy aspects, but also in all technical aspects, which represents one of the most crucial future investments for anaerobic digestion systems.

Nitrogen behaviour during thermal drying of mechanically dewatered biosludge from pulp and paper industry

An ongoing call to implement a circular economy is underway in the European Union, and a specific attention has been placed on the forest industry, which seeks additional recycling routes for its side streams, including biosludge. Biosludge is often dried and incinerated, thus wasting the nitrogen contained therein. This paper describes a study in which the release of nitrogen during thermal drying, the impact of the drying temperatures of 130°C, 180°C, and 210°C on the mass of ammonia released, and the potential for recovery of nitrogen from biosludge were examined. The results indicate that 1310-1730 mg kgTS^-1 of nitrogen was released, which corresponded to 56-74% of the soluble nitrogen in biosolids or 4.0-5.3% of the total nitrogen. Of this released nitrogen, 83-85% was identified in condensate and absorbing water, thus indicating a high potential for recovering nitrogen from biosludge.

Influence of the ultrasound pretreatment on anaerobic digestion of cattle manure, food waste and crude glycerine

To increase the production of methane, when cattle manure (CM) is digested, pretreatments can be applied and/or the manure can be co-digested with other wastes. In this research work, a mixture of CM, food waste (FW) and raw glycerine (Gly) in a proportion in weight of 87% CM, 10% FW and 3% Gly was digested, (a) without pretreatment and (b) with pretreatment by ultrasound, applying a sonication energy of 1040 kJ/kg total solids. Specific methane production was 290 L CH₄/kg volatile solids (VS) without pretreatment and 520 L CH₄/kg VS with pretreatment. With respect to the volumetric methane production, 1.07 L CH₄/L_reactor.day was produced in the first case, and in the second case, 1.98 L CH₄/L_reactor.day. We can conclude that the application of ultrasound pretreatment significantly improved the production of biogas.