Technology Overview

This chapter focuses on biogas production and upgrading technologies, an important area within Vietnam’s renewable energy sector. The process converts organic matter under anaerobic conditions into biogas rich in methane (CH₄) and carbon dioxide (CO₂), which can be used for heat and power generation or upgraded into biomethane.

Technical Characteristics

Industrial biogas plants typically use Continuous Stirred Tank Reactors (CSTR) to process pumpable biomass, such as sludge and wet industrial waste. These systems operate at temperatures of 35–40°C (mesophilic digestion) or 50–55°C (thermophilic digestion). In plants with upgrading systems, excess heat is reused to maintain digester temperature.

Conversion efficiency varies depending on biomass type and hydraulic retention time (HRT):

Biomass Type	DM Content	VS Ratio	Energy Input (GJ/ton VS)	Gas Output (GJ/ton VS)	Conversion Efficiency
Straw	85%	95%	17.4	9.5	55%
Maize	31%	95%	17.5	11.6	66%
Sugar beet	18%	95%	17.1	13.2	77%

Biogas upgrading technologies include amine scrubbing, water scrubbing, membrane separation, and pressure swing adsorption (PSA). Each method has distinct advantages and limitations. For example, amine scrubbing offers the highest methane retention efficiency but requires regeneration temperatures of 120–150°C.

Application in Vietnam

Currently, this technology has not been widely deployed in Vietnam, and there is no gas grid infrastructure to support biomethane distribution. However, given the country’s renewable energy potential, broader application is expected in the future.