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Anaerobic digestion (AD) technology has become increasingly important due to its contribution to sustainability and a circular bioeconomy. While AD technologies are widespread in developing countries, developed countries have mainly driven research. The aim of this research is to analyze the biogas sector development from the point of view of a developing country like Colombia. AD research ranges from laboratory mesophilic AD to psychrophilic full-scale digesters, which are intergrated with household farms as a thermal energy source for cooking, nutrient recycling for agriculture, and waste management. Research on agricultural waste substrates, inocula, and co-digestion has dominated the Colombian publications, while full-scale digesters performance research is incipient. A survey of installed digesters collected information about 996 systems and found that 79% were psychrophilic low-cost tubular digesters. Regulations for biogas were reviewed, and it was found that they are not adequate for low-cost digesters and are inherited from developed countries, ignoring the national context. Five case studies are presented on the characterization of AD technology experiences, analyzing barriers and opportunities for the technology. National networks that include farmers, NGOs, and academia are driven slowly by Colombia's widespread AD technology, mainly on small-to medium-scale farms.

This study carried out an anaerobic co-digestion treatment of cheese whey using cattle manure as a co-substrate. A co-digestion process was implemented in three tubular reactors, each one with a different organic load rate (0.5, 1.0 and 1.5 kg CODfed m−3digester day−1). A biochemical and microbiological analysis along the axial axis of each reactor showed that it was possible to obtain a phase separation with an organic load rate of 1.0 kg CODfed m−3digester day−1. The volatile fatty acid production phase takes place in the first reactor section and the consumption phase in the second section. Results from high-throughput sequencing analysis showed differences in the microbial communities between the samples of the three reactors for both eubacterial and archaeal compositions. In the reactor with intermediate organic loading rate, acetoclastic communities predominate, while at lower load, both acetoclastic and hydrogenotrophic communities are detected. Additionally, a microbial consortium stratification was observed.

Cheese whey (CW) is the main waste generated in the cheesemaking process and has high organic matter content and acidity. Therefore, CW disposal is a challenge for small to medium enterprises (SMEs) in the dairy industry that do not have any type of treatment plant. Anaerobic digestion (AD) is an attractive process for solving this problem. The aim of this research was to determine the biomethane and struvite precipitation potentials of CW from four dairy SMEs. First, changes in CW properties (organic matter and pH) were evaluated. Second, biomethane and struvite potentials were assessed using cattle slurry as inoculum. The organic matter in CW varied from 40 to 65gVS/kg, 65 to 140g COD/L, and 2 to 10g/L for VFAs depending on the sampling time and type of sample. The pH of the CW samples ranged from 3 to 6.5. In the anaerobic biodegradability analysis, methane yields reached 0.51 to 0.60L CH4/g VSadded, which represented electrical and caloric potentials of 54 and 108kWh/m3 for CW, respectively. Organic matter removal in all experiments was above 83%. Moreover, anaerobic digestates presented NH4+/PO43- molar ratios between 2.6 and 4.0, which are adequate for struvite precipitation with potential production of 8.5-10.4g struvite/L CW. Finally, the use of biogas as energetic supplement and struvite as soil fertilizer, represents economics saves of US$ 6.91/m3 CW and US$ 5.75/m3 CW in therms of electricity and fertilizer use, respectively. The energetic, agricultural and economic potentials, evidence that AD process is a feasible alternative for cheese whey treatment.