Landfill methane oxidation in soil and bio-based cover systems: a review

Mitigation of landfill gases has gained the utmost importance in recent years due to the increase in methane (CH4) emissions from landfills worldwide. This, in turn, can contribute to global warming and climatic changes. The concept of microbially mediated methane oxidation in landfill covers by using methanotrophic microorganisms has been widely adopted as a method to counter the rise in methane emissions. Traditionally, landfill soil covers were used to achieve methane oxidation, thereby reducing methane emissions. Meanwhile, the continual rise of CH4 emissions from landfills and the significant need to and importance of developing a better technology has led researchers to explore different methods to enhance microbial methane oxidation by using organic rich materials such as compost in landfill covers. The development and field application of such bio-based systems, explored by various researches worldwide, eventually led to more widely accepted and better performing cover systems capable of reducing CH4 emissions from landfills. However, the long-term performance of bio-based cover systems were found to be negatively affected by factors such as the material’s ability to self-degrade, causing CH4 to be generated rather than oxidized as well as the greater potential for forming pore-clogging exopolymeric substances. In order to design an effective cover system for landfills, it is essential to have a thorough understanding of the concepts incorporated into methodologies currently in favor along with their pros and cons. This review summarizes previous laboratory and field-scale studies conducted on various soil and bio-based cover systems, along with the modeling mechanisms adopted for quantifying CH4 oxidation rates. Finally, several issues and challenges in developing effective and economical soil and bio-based cover systems are presented.