Biological conversion and revalorization of waste methane streams

ABSTRACT

Methane-laden anthropogenic emissions are widely variable in terms of methane (CH₄) concentration depending on their source, ranging from <3% up to 80% of CH₄ as in biogas. Diluted emissions are commonly flared or directly vented to the atmosphere, while CH₄ concentrations exceeding 20% allow for energy production by direct combustion. Nevertheless, these practices entail a loss of potential energy and/or detrimental effects to the environment resulting from the release of greenhouse gases (CO₂ and CH₄) directly to the atmosphere. In this context, the implementation of low-cost, environmentally friendly biotechnologies aiming not only at abating CH₄ from these off-gases but targeting its revalorization represents a sustainable alternative from both an economic and environmental point of view. This review critically presents the state-of-the-art of biotechnologies devoted to the revalorization of anthropogenic CH₄ emissions, with a special focus on the bioconversion to methanol of the CH₄ contained in diluted streams and on the biological upgrading of the biogas to biomethane.

KEYWORDS:

• Biogas upgrading
• methanol
• waste methane revalorization

Acknowledgments

The authors acknowledge the support of MINECO and the European Programme FEDER under the project CTM2015-70442-R and Red NOVEDAR. The “Young Researchers Mobility Program” of the University of Valladolid is also gratefully acknowledged. Biomethanol production research at Columbia University is supported by the WERF Paul Busch Award to Kartik Chandran and by the National Science Foundation and the Bill and Melinda Gates Foundation.