The co-digestion of two problematic and available wastes, namely Organic Fraction Municipal Solid Waste (OFMSW) and biological sludge, was carried out in this work. Biochemical Methane Potential (BMP) tests are a useful tool for determining the best substrate and co-digestion configurations, however there are some methodologies destined to save costs and time from this process by using the theoretical final methane potential of a substrate from its organic composition. Besides there are some models capable not only of reproducing the methane curve behavior, but also of predicting final methane productions from the first days of experimentation. Methodologies based in the elemental composition for the determination of theoretical production fit better with the experimental results and behavior, nevertheless the Gompertz model was capable of predicting the final productivity within the 7th day of experiment, selecting at the same time the co-digestion of 80% OFMSW and 20% Biological sludge as the optimum.

The production of biogas from sulfate-rich materials under anaerobic digestion results in the formation of hydrogen sulfide (H2S). The recommended level of H2S in the produced biogas for direct combustion purposes is in the range of 0.02 to 0.05% w/w (200 to 500 ppm), therefore, desulfurization is required to avoid damages to combustion equipment and prevent the formation of sulfur dioxide (SO2) which is an acid rain precursor. It has been well documented that physical, thermal, and chemical desulfurization approaches suffer from high operation costs as well as waste production needing to be disposed of. Accordingly, a great deal of efforts has been put into biological methods because of being more environmentally friendly and more economically advantageous in comparison with the other techniques. Biotrickling filtration (BTF) and microaerobic desulfurization have shown a high potential for H2S removal at pilot- and large-scale plants. Despite all the progress made and the promising aspects keeping these methods at the core of interest, there are still challenges to be addressed. The present article attempts to briefly review and discuss the challenges and future prospects of BTF and microaerobic desulfurization.