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The use of the biogas process for the production of methane, which can be utilized as vehicle fuel or in power plants for electricity production, is strongly established both in Sweden and internationally. The microbiological process is traditionally used to reduce organic waste through digestion. Digested products are used as bio-fertilizers and thus constitute an important component in nutrient circulation, contributing to society’s efforts towards circularity and sustainability. There is an ambition to produce large amounts of biogas efficiently, which means that biogas facilities must be efficient and stable. They need to convert large amounts of substrates per reactor volume and time without disrupting the biological process. This depends, among other things, on how well the growth rate of the microorganisms that carry out anaerobic digestion can be optimized. Microorganisms require a balanced diet, where the availability of macro- and micronutrients is significant for the process. A balanced mixture of protein, fat, and carbohydrates in organic substrates normally provides sufficient levels of nitrogen, phosphorus, potassium, and calcium. However, in high-load reactors, the availability of micronutrients (e.g., iron, nickel, cobalt, tungsten, and selenium) has been shown to be limiting for process performance. By adding these substances, process performance can be improved. We have investigated the possibilities of adding the substances individually and in various combinations. The results show that this is a sustainable method, but both synergistic and antagonistic effects on biogas production occur. The project advanced this area with knowledge about the mechanisms that control the availability of trace metals in the anaerobic environment of the biogas reactors.

The results are presented in the dissertation "".

Funder: Swedish Energy Agency

Anaerobic organic matter degradation for biogas production is influenced by the characteristics of the organic substrate, particularly the resistance or reactivity of particulate organic matter (POM) towards microbial hydrolysis as the first step of the anaerobic degradation chain. The POM characteristics are also important for determining the fate of organic matter in agricultural soils where digestate (nutrient-rich rest materials after anaerobic degradation) are applied as fertilizers. This project applies 13C cross-polarization magic-angle spinning (CP-MAS) and two-dimensional 1H,13C heteronuclear single-quantum coherence (HSQC) nuclear magnetic resonance (NMR) spectroscopy to elucidate molecular structures within labile and recalcitrant POM fractions. This foundational information is important for exploring potential optimization strategies to enhance the degradability of underutilized POM for biogas production and the fate of organic matter in soil, where digestate is applied as a biofertilizer.

Relevant publications:

Funder: Swedish Energy Agency through Biogas Research Center