Algae, cyanobacteria and aquatic plants for production of biofuels

 

Overview

"Algae and aquatic biomass has the potential to provide a new range of "third generation" biofuels, including jet fuels. Their high oil and biomass yields, widespread availability, absent (or very reduced) competition with agricultural land, high quality and versatility of the by-products, their efficient use as a mean to capture CO₂ and their suitability for wastewater treatments and other industrial plants make algae and aquatic biomass one of the most promising and attractive renewable sources for a fully sustainable and low-carbon economy portfolio." (Source: European Algae Biomass Association - EABA).

A recent IEA Bioenergy report "State of Technology Review - Algae Bioenergy" (2017) gives  an international update on the status and prospects for using micro-and macroalgae as feedstocks as bioenergy feedstocks.

• Download the EBTP Value Chain Fact Sheet #7 Aquatic Biomass (353 Kb)

 

Cultivation of algae as advanced biofuel feedstocks

Algae have the potential to produce considerably greater amounts of biomass and lipids per hectare than terrestial biomass, and can be cultivated on marginal lands, so do not compete with food or other crops. Algae can be cultivated photosynthetically using sunlight for energy and CO₂ as a carbon source. They may be grown in Shallow lagoons or raceway ponds on marginal land (e.g. Sapphire Energy) or closed ponds (e.g. Green Star). Green Star also produces a micronutrient formula to greatly increase the rate of algal growth.

A number of closed photobioreactors are being investigated, including: Horizontal tubes (e.g. AlgaeLink NV), Vertical (e.g. Ecoduna), Thin film, Open/Closed systems (e.g. Parabel, Cellana). See also Subitec, Germany.

Productivity is higher in the controlled, contained environment of a photobioreactor, but capex and opex are also both substantially higher than for open systems. Significant investment in research is required before high levels of productivity can be guaranteed on a commercial scale.

Algae to biofuels plants may be developed on land adjacent to power stations, for converting the carbon dioxide from exhausts into fuel.

Conversion of algae to biofuels

Algae may be used to produce biofuels in several ways:

• Conversion to bioethanol (e.g. Algenol)
• Exraction of oils (e.g. SGI, Solixalgredients, Sapphire Energy, Algasol).
• Production of oils from feedstock via dark fermentation (e.g. Solazyme)
• Conversion of whole algae to biocrude via pyrolysis
• "Green crude" (e.g. Sapphire Energy, Muradel)
• Algal biorefinery - biofuels and other products (Parabel, Cellana)

Following extraction, algal oils may be further refined (e.g. by hydrocracking and hydrogenation) to produce gasoline or jet fuels.

Example: Botyrococcus sp. (used for oil extraction)

Algal Biorefineries

In addition to producing oils, algae are rich sources of vitamins, protein and carbohydrates. The following steps have been identified for development of microalgae biorefineries.

• Development of mild and efficient cell disruption, extraction and fractionation technologies
• Effective technologies for separation of carbohydrates, proteins and lipids
• Lipid /oil refining technologies
• Improvement of energy consumption and environmental performance, decrease of capital costs
• Integrate knowledge & facilities for oil, food and fine chemical industry
• Biomass provision (quantity and quality)

Source: Wageningen University, Netherlands

Associations

EABA - European Algae Biomass Association aims to act as a catalyst for fostering synergies among scientists, industrialists and decision makers in order to promote the development of research, technology and industrial capacities in the field of algae.

Algal Biomass Association (US) - promotes the development of viable commercial markets for renewable and sustainable commodities derived from algae.