The Biofuel (Dis)advantage
Currently most biocrops, used to make biofuel, require significant chunks of land which could instead be used to grow food. This competition aspect increases the production cost and presents an additional strain on food production capacity.
The three main biofuels are
Conversion to biodiesel and bioethanol require significant energy inputs. Conversion to biogas is low-energy since the microbes do the 'work', but conditions need to be kept optimal for organisms to thrive.
Algal biofuel is seen by the energy industry as a strong potential alternative to land-based biocrops. Huge investment in production of biodiesel, bioethanol and biogas using algae is underway, and these are being put to use in various industries, such as to fuel new types of engine for transport and to produce electricity.
Currently most biocrops, used to make biofuel, require significant chunks of land which could instead be used to grow food. This competition aspect increases the production cost and presents an additional strain on food production capacity.
The three main biofuels are
- Biodiesel, using crops with high lipid content
- Bioethanol, using crops with high sugar/starch content
- Biogas, (methane) produced by microbes from anaerobic digestion of organic material
Conversion to biodiesel and bioethanol require significant energy inputs. Conversion to biogas is low-energy since the microbes do the 'work', but conditions need to be kept optimal for organisms to thrive.
Algal biofuel is seen by the energy industry as a strong potential alternative to land-based biocrops. Huge investment in production of biodiesel, bioethanol and biogas using algae is underway, and these are being put to use in various industries, such as to fuel new types of engine for transport and to produce electricity.
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The American Centre for Life-Cycle Assessment (ACLCA) gives a comparison of four common biocrops, including algae:
Click to enlarge
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Biocrops. Image courtesy of Biomass Energy Centre
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The main barrier to production of algae continues to be its very high cost of production, correlating to a net energy loss, arising from the vast quantities of:
Flocculation is also used, but this requires the addition of chemicals (flocculants) which remain held in the algae flocks, rendering them unsuitable for anearobic digestion.
Economic incentives are strengthened if these prohibitive resource and energy requirements (above) can be:
- Fresh water
- Fertiliser
- Land
- Energy
Flocculation is also used, but this requires the addition of chemicals (flocculants) which remain held in the algae flocks, rendering them unsuitable for anearobic digestion.
Economic incentives are strengthened if these prohibitive resource and energy requirements (above) can be:
- offset by using waste water (be it agricultural, industrial or domestic) to provide the environment (high in nitrates and phosphates) in which algae can thrive, and
- an efficient, low energy extraction system to reclaim the algae following treatment of waste.
The latter will Currently biofuel is comprised of three
Eutrophication
The process of eutrophication is triggered when unnaturally high concentrations of fertiliser, high in nitrates and phosphates enter water bodies and systems, causing algal blooms. This fertiliser often originates from farmland where it is applied to crops to ensure high yield growth. Uptake rates are in the region of 55 - 70% (Defra Fertiliser Manual), with the remainder becoming mobile through rainfall run-off.
The rapid growth of algae in waterways blocks out sunlight and depletes oxygen levels (known as hypoxia) in the water. Unable to photosynthesise, algae at the bottom begin to die, creating toxic conditions for marine life such as fish and aquatic mammals. Health problems are commonly associated with certain algae species, such as some forms of Blue-Green Algae (indistinguishable from its benign relatives) which release potent toxins on cell death.
Governments and water companies face challenges to restrict eutrophic water infiltrating into deep freshwater aquifers, as well as the problem of treatment at surface level to remove toxins from open water supply systems.
The process of eutrophication is triggered when unnaturally high concentrations of fertiliser, high in nitrates and phosphates enter water bodies and systems, causing algal blooms. This fertiliser often originates from farmland where it is applied to crops to ensure high yield growth. Uptake rates are in the region of 55 - 70% (Defra Fertiliser Manual), with the remainder becoming mobile through rainfall run-off.
The rapid growth of algae in waterways blocks out sunlight and depletes oxygen levels (known as hypoxia) in the water. Unable to photosynthesise, algae at the bottom begin to die, creating toxic conditions for marine life such as fish and aquatic mammals. Health problems are commonly associated with certain algae species, such as some forms of Blue-Green Algae (indistinguishable from its benign relatives) which release potent toxins on cell death.
Governments and water companies face challenges to restrict eutrophic water infiltrating into deep freshwater aquifers, as well as the problem of treatment at surface level to remove toxins from open water supply systems.
Wastewater Treatmemt
The preservation of high quality freshwater supplies is more important for sustainable development than reducing the energy inputs for treatment. Currently a vast amount of energy is spent during the treatment process, removing things like algae through processes such as dissolved air flotation, in order to achieve the high quality standards required.
Algae has the potential to treat wastewater by taking up contaminants passively and without significant energy inputs. However, currently the extraction of algae itself requires large amounts of energy through unsustainable techniques - making the addition of algae for treatment not viable at this time.
A conceivable closed loop system would be: algae used to treat wastewater, then being removed to produce bioenergy to run the treatment plant. A study of an Austrian Wastewater Treatment Plant (WWTP) found that electricity generation of 11% of the total energy captured in influent organics was sufficient to run the entire plant, suggesting that WWTPs will soon take on the role of resource recovery systems instead of nutrient removal ones.
The preservation of high quality freshwater supplies is more important for sustainable development than reducing the energy inputs for treatment. Currently a vast amount of energy is spent during the treatment process, removing things like algae through processes such as dissolved air flotation, in order to achieve the high quality standards required.
Algae has the potential to treat wastewater by taking up contaminants passively and without significant energy inputs. However, currently the extraction of algae itself requires large amounts of energy through unsustainable techniques - making the addition of algae for treatment not viable at this time.
A conceivable closed loop system would be: algae used to treat wastewater, then being removed to produce bioenergy to run the treatment plant. A study of an Austrian Wastewater Treatment Plant (WWTP) found that electricity generation of 11% of the total energy captured in influent organics was sufficient to run the entire plant, suggesting that WWTPs will soon take on the role of resource recovery systems instead of nutrient removal ones.
