Enhancing performance in anaerobic high-solids stratified bed digesters by straw bed implementation.

Area of Science:

• Biotechnology and Bioengineering
• Environmental Science and Engineering
• Waste Management and Resource Recovery

Background:

• Anaerobic digesters are suitable for small-scale, low-technology applications.
• Stratified bed digesters offer design flexibility.
• Wheat straw can serve as a starter material and biofilm support.

Purpose of the Study:

• To evaluate the performance of anaerobic high-solids single-stage stratified bed digesters using wheat straw.
• To assess the digester's capacity for direct feeding and its impact on bed permeability.
• To determine biogas production rates and methane yields with different feedstocks.

Main Methods:

• Utilized wheat straw as the starter material in a stratified bed digester.
• Employed green mass and sugar beet tops as feedstocks in fed-batch tests.
• Conducted pilot- and laboratory-scale experiments to measure biogas production and methane yield.
• Monitored bed permeability and performance over a 200-day trial.

Main Results:

• The straw bed acted as a biofilm support and particulate filter, allowing direct onset of high-solids batch loads (7 kg VS m(-3)).
• Consistent bed permeability was maintained at a superficial flow velocity of 1 m d(-1).
• Fed-batch tests yielded average biogas production rates of 1.2-1.4 m(3) m(-3) d(-1) and methane yields of 0.31-0.36 m(3) kg(-1) VS(added).

Conclusions:

• Anaerobic stratified bed digesters with wheat straw are effective for small-scale biogas production.
• The system demonstrates robustness, maintaining performance despite straw bed compaction.
• This technology presents a viable option for decentralized waste treatment and energy generation.