Algae biofuels promise greater productivity, and can be grown on nonarable land, and with mostly non-potable water. However, as with any new technology—especially in the biofuels space— many questions about its technical potential and sustainability remain.

Sustainably Producing Algae Biofuels for a Clean Energy Future

Cai Steger | Natural Resources Defense Council

As America looks for ways to reduce global warming pollution and fuel the clean energy future, innovative approaches to clean energy development are getting more attention. Recently, many scientists, investors and entrepreneurs have begun looking at algae as a new source for biofuel. 
Algae biofuels promise greater productivity, and can be grown on nonarable land, and with mostly non-potable water. However, as with any new technology—especially in the biofuels space— many questions about its technical potential and sustainability remain. 
To address some of these questions, the Natural Resources Defense Council (NRDC) recently published research analyzing algae as a potential new energy source in an effort to determine its environmental impact and viability as the basis for a next generation clean fuel.
This new report “The Promise of Algae Biofuels” was designed to both identify some of the key ecological issues potentially present across stages of production, and summarize known and unknown environmental impacts of each algae biofuel production process. 
Having spent the past year knee deep in algae, NRDC now describes its perspective as “cautiously optimistic”.   If developed sustainably, NRDC believes algae feedstock may be used to produce large quantities of biofuels with potentially minimal environmental impacts. However, to do so sustainably, the industry must now build on the data currently available and fill remaining information gaps regarding environmental performance. Otherwise, as with earlier generations of biofuel technologies, the economic, technical and political challenges brought on by unsustainable production practices could derail algae as a feedstock long before it has reached its fullest potential. 
The full algae biofuels production process will have a range of environmental implications, depending on how each production pathway develops.
Per NRDC’s report, production generally consists of four linked processes, algae cultivation, biomass harvesting, algal oil extraction, and oil and residue conversion, with different options within each broad category.
Algae cultivation at commercial scale (where algae is grown in open or closed systems for downstream usage) could have significant environmental consequences, based on how water, nutrients, land, and light are supplied and managed. At a minimum, criteria for sustainable cultivation should consider the impact of water, land, and genetically modified organism (GMO) usage on biodiversity and ecosystem health, as well as the environmental impacts of infrastructure fabrication, materials toxicity, electricity demands, and waste treatment.
Harvesting involves recovering, dewatering, and drying algal biomass. Most recovery processes require chemical or mechanical manipulation to separate the biomass from the process wastewater. The criteria for sustainable biomass harvesting should consider the potential toxicity of chemical additives, environmental management of output water, and the energy and carbon balance implications of energy-intensive drying techniques.
Algal oil extraction (removing oil from the algae biomass) can be achieved via a number of techniques, but there is limited information about the chemical and energy inputs in this process. The criteria for sustainable oil extraction should consider energy inputs and potential environmental toxicity of chemical solvents.
Oil and residue conversion pathways have been employed in conventional biofuel refining for some time, so data are available, although not necessarily related specifically to algae biofuels. The criteria for sustainable conversion should consider potential energy usage and the handling of low-value coproducts or byproducts. In the near term, industry may need to embrace biological services (e.g., wastewater treatment) and high-value nonfuel coproducts to make algae biofuels economically viable.
NRDC also examined potential areas of ecological and biological concern that the biofuels industry should fully address, including water, land, soil and air and also looked at issues surrounding the energy and carbon balance of algae biofuels. Based on NRDC research, the key to making algae a successful biofuel is reducing impacts on primary ecological resources—water, land, soil, biodiversity, and air—as well as balancing the energy produced against the carbon used in the production process.
The effect of algae biofuel production on regional water sources is not yet fully understood. Fortunately, it appears that early emphasis by the algae biofuels industry on water impact could mitigate many potential issues. Water-related concerns include aggregate water consumption, systems discharge and water quality, and reduction of groundwater infiltration. The ability of algae to thrive in and treat wastewater and potentially eliminate the need for agriculturally-based biofuels offers one promising path to mitigate some water issues, but further study and technology development is needed.
Algae biofuels may however have a strong advantage over agriculture-based biofuels, as they can be produced on non-arable land. However, claims regarding yield per acre are often exaggerated and certain algae cultivation processes could have far more land impact than others. For example, open systems will likely have a relatively larger land use footprint than other systems, while heterotrophic systems (which use sugar to grow algae) could have significant indirect land use impacts.
As with all industrial systems using hazardous substances, algae production could contribute to soil contamination unless non-chemical methods are used for harvesting and other processes. Poisoning soil with salt is also a concern for algae cultivated in briny or brackish water. Overall biodiversity could be threatened by producing algae biofuels unsustainably (e.g., through land transformation, water and soil contamination, air pollution, and use of alien species).
Similar to soil and biodiversity, the pathway of biofuel production and the technologies used will determine impact on air quality. One potential area for future research is the impact of evaporation from open-pond cultivation on local and regional humidity, and local ecosystems.
The potential energy and carbon balances of algae biofuels are highly uncertain calculations, and range widely depending on production system, type of biofuel produced, and energy savings realized by the coproducts. It is critical to consider the net impact of greenhouse gasses (GHGs), which includes all direct and indirect inputs and outputs from all production processes employed.
Finally, NRDC’s report recommends a number of steps that regulators/policymakers and industry can take to proactively encourage sustainable algae biofuel production.
From a regulatory and policy standpoint, key steps include clarifying roles and responsibilities within government agencies, establishing information resources, specifying sustainability metrics and industry standards, encouraging industry collaboration and assisting in life cycle analysis (LCA). The algae industry can proactively address sustainability issues by conducting and publishing techno-economic and life cycle analyses, water balances, and energy and carbon balances; where feasible and adopting low-impact development, operations, and maintenance practices. Finally, together and separately, the public and private sector should use the information from various sustainability assessments to guide research and development to help algae fuels avoid and mitigate environmental impacts.
Although the process will not be simple, and the environmental implications must be fully addressed, it appears algae biofuels may hold promise as a clean energy fuel of the future.

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