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Abstract For biogas production, different renewable feedstocks, e.g., feces, manure, silage, industrial by-products, and municipal waste, can be used. Biogas production from various renewable feedstocks has positive socioeconomic and environmental impact. In Europe, biogas is mainly used for generating heat and electricity. It consists of methane (55–70% by volume), carbon dioxide (30–45% by volume), and small amounts of other compounds. In some cases, biogas is upgraded to pure biomethane and utilized as vehicle fuel, instead of fossil fuels, thus reducing the emissions of greenhouse gases. Biomethane can also serve as a platform chemical in chemical and biochemical synthesis to produce value-added products. The additional positive effects of anaerobic digestion of animal manure and slurries are organic waste degradation, reducing odors, and pathogens. Digestate, obtained as a by-product of anaerobic digestion, is rich in nutrients and therefore is applied as fertilizer in agriculture. Biogas production in Croatia is mainly based on manure and by-products from agriculture, food industry, and slaughterhouses. The obtained biogas is mostly used for electricity and heat generation. Potential for large-scale biogas production in Croatia is still insufficiently used, although various renewable feedstocks are available. More rational and focused management of lignocellulosic residues, animal excrements, food processing by-products, and biodegradable fraction of municipal waste could contribute to the development of Croatian biogas sector. Biogas production in Croatia can be affected by the changes of animal breeding capacity due to the struggle to cope with the European Union (EU) standards and prices. Concerning large unused agricultural areas, great potential lies in their rational exploitation for fast-growing biomass, e.g., for energy crops or perennial grasses. This review will discuss the potential of biogas in the industrial and farming sector, current state of biogas production, and various key drivers and barriers influencing biogas production in Croatia.

Abstract Background Lytic polysaccharide monooxygenases (LPMO) release a spectrum of cleavage products from their polymeric substrates cellulose, hemicellulose, or chitin. The correct identification and quantitation of these released products is the basis of MS/HPLC-based detection methods for LPMO activity. The duration, effort, and intricate analysis allow only specialized laboratories to measure LPMO activity in day-to-day work. A spectrophotometric assay will simplify the screening for LPMO in culture supernatants, help monitor recombinant LPMO expression and purification, and support enzyme characterization. Results Based on a newly discovered peroxidase activity of LPMO, we propose a fast, robust, and sensitive spectrophotometric activity assay using 2,6-dimethoxyphenol (2,6-DMP) and H2O2. The fast enzymatic assay (300 s) consists of 1 mM 2,6-DMP as chromogenic substrate, 100 µM H2O2 as cosubstrate, and an adequate activity of LPMO in a suitable buffer. The high molar absorption coefficient of the formed product coerulignone (ε 469 = 53,200 M−1 cm−1) makes the assay sensitive and allows reliable activity measurements of LPMO in concentrations of approx. 0.5–50 mg L−1. Conclusions The activity assay based on 2,6-DMP detects a novel peroxidase activity of LPMO. This activity can be accurately measured and used for enzyme screening, production, and purification, and can also be applied to study binding constants or thermal stability. However, the assay has to be used with care in crude extracts, because other enzymes such as laccase or peroxidase will interfere with the assay. We also want to stress that the peroxidase activity is a homogeneous reaction with soluble substrates and should not be correlated to heterogeneous LPMO activity on polymeric substrates.