Table 3.

Advantages and disadvantages of various sulfur control approaches.

Method	Advantages	Disadvantages	Economic considerations based on capital costa	References
Micro-aerobic process	-The rate of hydrolysis of both carbohydrates and protein is enhanced by 21–27 and 38–68%, respectively. -Improves the degradation process of COD -No catalyst is required	-If not well controlled can lead to the accumulation of lactic acid.	Lower operational cost equivalent to 0.0019 EUR/m3 of biogas treated	[167,168,55]
Precipitation process	-Metals such as Fe and Zn can be recovered for the precipitating process.	-The method requires the use of chemicals, which are hence costly. -Minimum selectivity	No data	[169,60]
Adsorption process	-Adsorbents materials can be functionalized to modify their surface properties for the adsorption process	-The adsorption of H2S is mostly affected by carbide formation during carbonization. -Limited to the lower concentration of H2S	Relatively expensive, with an estimated cost of US$2.3 per m3 of biogas	[170,2,171]
Stripping	-It is simple to use	-High energy consumption. -Costs are often involved in building the stripping tower	No data	[172,173]
Wet scrubbing	-Simple to operate -Strong adaptability and high efficiency	-High energy demand for the regeneration process -High corrosiveness of equipment surfaces	When employing NaOH, it costs roughly US$2.38/m3.	[174,171,134]
Aerobic biological technology	-Energy costs are reduced because the process can take place at ambient temperature	-It is a time-consuming method	No data	[175,176]
Biofiltration	-No harmful byproducts are being generated. -High removal efficiency -Simple to operate.	-The design is not simple and inquires about some operational parameters that need to be optimized.	High treatment cost nearly US$1.5/m3 of biogas	[145,165]

^aCost data based on estimates for the year 2015–2019 with currency conversion of 1EUR to US $1.12.