How to Use Algae for Small-Scale Biogas Production

How to Use Algae for Small-Scale Biogas Production

What is Algae Biogas?

Algae biogas is a renewable energy source produced by anaerobic digestion of algae biomass. In this process, algae are grown in ponds or photobioreactors, harvested, and then fed into an anaerobic digester. Inside the digester, bacteria break down the algae biomass in the absence of oxygen, releasing biogas as a byproduct.

The main components of algae biogas are methane (CH4) and carbon dioxide (CO2). Methane is the valuable component that can be used similarly to natural gas for heating, electricity generation, and transportation fuel. Algae biogas typically has 50-70% methane content, compared to 60-80% for natural gas.

Benefits of Using Algae for Biogas Production

There are several advantages to using algae for biogas production compared to other feedstocks:

Algae Species for Biogas Production

Many different algae species can be used for biogas production. Some of the most suitable ones include:

Ideally, fast growing species with high carbohydrate or lipid content are preferred, as these components are easiest to break down into biogas. Local species adapted to the climate should be chosen.

Algae Cultivation Systems

Algae can be cultivated using open ponds or closed photobioreactor systems:

Open Ponds


For small-scale biogas production, simple open ponds like raceways may be most economical.

Biogas Digester Design

Common digester designs suitable for small-scale algae biogas include:

For algae biogas, wet digestion systems like complete mix or fixed dome digesters are likely most appropriate. The digesters should be sized to provide a minimum 15-20 day hydraulic retention time. Heating the digester can increase biogas production in cold climates.

Algae Harvesting and Pre-Treatment Methods

Before feeding algae into the anaerobic digester, it needs to be concentrated and harvested from the cultivation ponds or photobioreactors. Some options include:

If the raw algae has a solid content under 5-10%, it may require concentration before anaerobic digestion to avoid digester volumes becoming too large. Simple gravity settling or flocculation are likely suitable pre-treatment methods at small-scale.

Key Factors Affecting Biogas Production

To maximize biogas production from algae, some key factors need to be considered:

Carefully controlling these parameters allows algae biogas systems to reach their full potential methane production.


Algae are an excellent renewable feedstock for small-scale biogas production. With modest investment in open ponds, digesters, and harvesting equipment, energy independence through homegrown methane fuel can be achieved. Correctly sizing the system and optimizing operational parameters will lead to long-term success. Algae biogas provides a sustainable energy solution while making use of wastewater resources.