324 Marine Macro- and Microalgae: An Overview
Predicting economic and environmental impacts: examples from Life Cycle Assessments
On several occasions throughout this chapter we have noted that that the economic and environmental
impacts of microalgal technology are small (whether positive or negative) because of the small scale of
microalgal production at present. However, we predict that the scale of production will increase as new
strains (wild type and GMO) and new production technologies are developed: we see a future in which
more nutritional, environmental, and energy products from microalgae will be economically attractive.
In the meantime, and even at small scale, localized positive economic benefits of microalgal technology
have been documented (see section on Economic impacts, above).
Technoeconomic analysis and Life Cycle Assessments (LCAs) are modeling tools that can help
us understand what those impacts might be at larger-than-present scale. One can ask, for the different
proposed products and processes, whether they will be economically feasible, whether the various
balances of energy, water, CO 2 , and nutrients are positive or negative, whether the environmental impacts
will be acceptable and whether the processes are sustainable. Several such studies have been published
over the last few years to study different aspects of microalgal production although mostly regarding
microalgal biofuel production. This is probably the case because biofuel production would be expected
to occur at a scale where environmental and economic impacts would be expectedly large. Still, some of
their findings are useful and applicable to microalgal production in general.
It is generally agreed that large scale microalgal production needs large amounts of nutrients, CO 2 ,
and water. It will also require large amounts of energy (from mixing of cultures to dewatering and
downstream processing of the biomass). In reviewing this chapter, one can see that we have described
processes where microalgae can replace other products at large scale: e.g., microalgal proteins, oils, and
whole biomass to replace fishmeal and nutritional oils and oils and biomass to replace fossil fuels. So
the questions are not simply how much CO 2 , water, nutrients, and energy microalgal products require
but how that compares to that needed by the products and processes they replace. The assumption is that
consuming more CO 2 , less water, less energy, and fewer nutrients are desirable characteristics.
Detailed LCAs comparing microalgal feed ingredients versus those of agricultural and animal origin
are lacking while there are numerous ones comparing microalgal fuel precursors to fossil fuels, including
a recent effort in which Synthetic Genomics was a participant (Vasudevan et al. 2012). In that study,
special attention was paid to to GHG (greenhouse gas) emissions, freshwater consumption, and energy
inputs and outputs. Depending on the technology set chosen, that study determined that microalgal
biofuels could have a negative or positive energy balance, emit more or less GHG than conventional
fuels and, when using brackish or salt water, consume about as much freshwater as fossil fuels. Replacing
dry extraction with wet extraction technology was identified as a leading hurdle that, if overcome, would
result in large (> 50%) reductions in GHG emissions and a favorable energy balance.
A similar conclusion was reached by Sander and Murthy (2010). They identified the amount of energy
needed to process microalgal biomass into useable components as a major obstacle. They considered that
if the energy needed for dewatering could be minimized by using wet-based processes based on enzymedriven degradation of the microalgal biomass the energy balance for microalgae based products would
be favorable. Another option is that suggested by Taylor et al. (2013). In that study (that is, Taylor et al.
2013), the authors propose to use non-fossil renewable energy, specifically concentrated solar power
(CSP) and solar drying, for the energy-requiring processes such as providing mixing to the cultures,
dewatering, etc. By doing so, the process can be CO 2 negative as well as energetically positive. Shirvani
et al. (2011) also reached a similar conclusion; they suggest the need to decarbonize heat, electricity, and
other energy requirements to produce, for example, fertilizers. Vasudevan et al. (2012) noted that fresh
water consumption is expected to be similar for microalgal biofuels when compared to fossil fuels. Yang
et al. (2011) considered the fresh water footprint when different types of water were used (fresh, salt,
and waste) under different levels of recycling. Their results indicate that microalgae are very competitive
with other types of agricultural feedstocks. Clarens et al. (2010) found that other biofuels feedstocks may
actually have a lower environmental impact than microalgae but that the ability to utilize flue gasses and
waste waters would improve their performance. They also found that microalgae are superior to other
feedstocks when land area use and eutrophication potential are considered.
Predicting economic and environmental impacts: examples from Life Cycle Assessments
On several occasions throughout this chapter we have noted that that the economic and environmental
impacts of microalgal technology are small (whether positive or negative) because of the small scale of
microalgal production at present. However, we predict that the scale of production will increase as new
strains (wild type and GMO) and new production technologies are developed: we see a future in which
more nutritional, environmental, and energy products from microalgae will be economically attractive.
In the meantime, and even at small scale, localized positive economic benefits of microalgal technology
have been documented (see section on Economic impacts, above).
Technoeconomic analysis and Life Cycle Assessments (LCAs) are modeling tools that can help
us understand what those impacts might be at larger-than-present scale. One can ask, for the different
proposed products and processes, whether they will be economically feasible, whether the various
balances of energy, water, CO 2 , and nutrients are positive or negative, whether the environmental impacts
will be acceptable and whether the processes are sustainable. Several such studies have been published
over the last few years to study different aspects of microalgal production although mostly regarding
microalgal biofuel production. This is probably the case because biofuel production would be expected
to occur at a scale where environmental and economic impacts would be expectedly large. Still, some of
their findings are useful and applicable to microalgal production in general.
It is generally agreed that large scale microalgal production needs large amounts of nutrients, CO 2 ,
and water. It will also require large amounts of energy (from mixing of cultures to dewatering and
downstream processing of the biomass). In reviewing this chapter, one can see that we have described
processes where microalgae can replace other products at large scale: e.g., microalgal proteins, oils, and
whole biomass to replace fishmeal and nutritional oils and oils and biomass to replace fossil fuels. So
the questions are not simply how much CO 2 , water, nutrients, and energy microalgal products require
but how that compares to that needed by the products and processes they replace. The assumption is that
consuming more CO 2 , less water, less energy, and fewer nutrients are desirable characteristics.
Detailed LCAs comparing microalgal feed ingredients versus those of agricultural and animal origin
are lacking while there are numerous ones comparing microalgal fuel precursors to fossil fuels, including
a recent effort in which Synthetic Genomics was a participant (Vasudevan et al. 2012). In that study,
special attention was paid to to GHG (greenhouse gas) emissions, freshwater consumption, and energy
inputs and outputs. Depending on the technology set chosen, that study determined that microalgal
biofuels could have a negative or positive energy balance, emit more or less GHG than conventional
fuels and, when using brackish or salt water, consume about as much freshwater as fossil fuels. Replacing
dry extraction with wet extraction technology was identified as a leading hurdle that, if overcome, would
result in large (> 50%) reductions in GHG emissions and a favorable energy balance.
A similar conclusion was reached by Sander and Murthy (2010). They identified the amount of energy
needed to process microalgal biomass into useable components as a major obstacle. They considered that
if the energy needed for dewatering could be minimized by using wet-based processes based on enzymedriven degradation of the microalgal biomass the energy balance for microalgae based products would
be favorable. Another option is that suggested by Taylor et al. (2013). In that study (that is, Taylor et al.
2013), the authors propose to use non-fossil renewable energy, specifically concentrated solar power
(CSP) and solar drying, for the energy-requiring processes such as providing mixing to the cultures,
dewatering, etc. By doing so, the process can be CO 2 negative as well as energetically positive. Shirvani
et al. (2011) also reached a similar conclusion; they suggest the need to decarbonize heat, electricity, and
other energy requirements to produce, for example, fertilizers. Vasudevan et al. (2012) noted that fresh
water consumption is expected to be similar for microalgal biofuels when compared to fossil fuels. Yang
et al. (2011) considered the fresh water footprint when different types of water were used (fresh, salt,
and waste) under different levels of recycling. Their results indicate that microalgae are very competitive
with other types of agricultural feedstocks. Clarens et al. (2010) found that other biofuels feedstocks may
actually have a lower environmental impact than microalgae but that the ability to utilize flue gasses and
waste waters would improve their performance. They also found that microalgae are superior to other
feedstocks when land area use and eutrophication potential are considered.