Environmental impact of biogas: A short review of current knowledge

Abstract

The social acceptance of biogas is often hampered by environmental and health concerns. In this study, the current knowledge about the impact of biogas technology is presented and discussed. The survey reports the emission rate estimates of the main greenhouse gases (GHG), namely CO, CH and NO, according to several case studies conducted over the world. Direct emissions of gaseous pollutants are then discussed, with a focus on nitrogen oxides (NO); evidences of the importance of suitable biomass and digestate storages are also reported. The current knowledge on the environmental impact induced by final use of digestate is critically discussed, considering both soil fertility and nitrogen release into atmosphere and groundwater; several case studies are reported, showing the importance of NH emissions with regards to secondary aerosol formation. The biogas upgrading to biomethane is also included in the study: with this regard, the methane slip in the off-gas can significantly reduce the environmental benefits.

A Review of the Chemistry of Anaerobic Digestion: Methods of Accelerating and Optimizing Process Efficiency

“…This makes a symbiosis necessary for the acetogenic and methanogenic bacteria to use the H 2 released in the process. The acetogenesis stage of AD is equally vital because it reflects the efficiency of biogas production since approximately 70% of CH 4 is formed through reduction of CH 3 COO − , which is the key intermediary product of the digestion process; approximately 25% of CH 3 COO − and about 11% of H 2 are formed in the acetogenesis stage of AD [43]. However, it is vital to clearly state that the VFAs produced in the previous stage are further broken down in this stage by obligate hydrogen-producing acetogenic microorganisms for the production of CH 3 COOH, CO 2 and H 2 .…”

“…This technology (AD) has a positive net energy production rate and the CH 4 gas produced from the process also has the tendency to replace fossil fuels. In fact, if properly handled, AD systems have no negative effect on human health or the environment [3]. The advantages of AD systems are well documented and some of them are summarized in Table 1.…”

Comparative assessment of different air‐conditioning systems for nearly/net zero‐energy buildings

“…Here, solar PV based generation helps for carbon neutrality. It may be envisaged that the use of biogas‐based system is carbon neutral . In this study, solar PV is used to supply energy as per the demand.…”

“…It may be envisaged that the use of biogas-based system is carbon neutral. 37 In this study, solar PV is used to supply energy as per the demand. However, solar PV system is unable to continuously fulfil building's energy demand due to some constraints (eg, space, solar radiation availability).…”

Underestimates of US emissions and global implications for industrializing animal agriculture

“…Recouping an investment in new equipment can make producing larger quantities attractive. Producing larger quantities, in turn may entail concentrating animals and consolidating their manure production in one large place (Paolini et al, 2018). Following the advice to implement sustainable intensification within animal systems may often, in practice, involve moving across animal systems, and veering into industrial production.…”