Biogas production from cheese whey: Past, present and future

Cheese whey is a type of dairy wastewater that is either discharged directly into the environment or the local sewer, treated with the primary object to meet effluent discharge limits, or used as a resource to produce, for example, biofuels, single cell proteins, animal feed after condensation, sweetener after crystallization of lactose, xanthan gum, glycerol and 2,3 butanediol upon fermentation. This review has been dedicated to the production of biofuels, specifically biogas, from cheese whey. We aim to provide the reader with a brief account of how knowledge in the field of biogas production from cheese whey effluents has evolved, the current status quo, and identify areas that should be addressed in the near future.

Based on the review of ca. 100 research papers published over the past 25 years following facts were extracted: A large body of knowledge exists at lab and pilot-scale. It has been shown that cheese whey wastewater can be used either as a primary or co-substrate for the production of biomethane and biohydrogen. Amongst the reactors studied, high-rate anaerobic digesters can be operated at organic loading rates up to 40 g COD L-1 d-1 with relatively low hydraulic retention times (0.5 – 10 d). The 1980ies have seen the implementation of the first fully integrated systems in New Zealand and Ireland. It was also concluded that anaerobic treatment of full-strength cheese whey, despite COD removal efficiencies of up to 99 %, cannot meet the
stringent discharge criteria set forth in most countries thus requiring an aerobic polishing step.

As the biogas technology reaches technical maturity and enters the commercial stage in the dairy industry, more data and reliable statistics are needed to evaluate the economical and operational feasibility at the industrial scale, including how we deal with the anaerobic digester effluent. Life cycle and carbon footprint assessments of the overall treatment process are to be carried out before it can be promoted as a technology that can contribute towards sustainable development and a more environmentally friendly agroindustry.

Cooperation and promotion should be encouraged among agroindustries, government and national research institutes as well as providers of technology, operators and clients of digestion products. Consequently, decision makers will be able to choose the best technologies and options to promote the digestion products. It should also be recognized that the competition between different processes exploiting cheese whey as a resource will continue due to technological advances.