Present and Future Economic and Environmental Impacts of Microalgal Technology 307
production is appreciated. We predict that from this base of understanding the industry will enter a phase
of steady, if not explosive, growth.
Environmental impacts
Like any other economic activity, algal technology can be expected to have environmental impacts. Large
scale micro-algae cultivation is dependent on water sources (either fresh or salt water), inorganic nutrients
(including nitrogen, phosphorus, iron, potassium, and other trace metals), and CO 2 and energy. In this
section, we will explore the pros and cons of various nutrient and water sources, and how algae compare
to terrestrial sources. For the most part, estimates of water and nutrient usage used here are based on
current algae biomass productivities and lipid content. Improving either of these parameters has direct
effects on improving the environmental and economics of microalgae production. Possible methods for
improving productivity and lipid content will be discussed later in this chapter.
Water
Fresh water footprint
Successful cultivation of algae is dependent on consistent supply of quality water at a predictable cost.
Algae biofuel production is often touted for the fact that they can grow in seawater or brackish water,
and therefore do not have to compete with agricultural uses. While some current algae production does
require fresh water, we will only consider the case of marine algae here, as that is the most pragmatic
approach at commodity scales. However, depending on the cultivation system, and location of production,
there will be significant water demand to compensate for harvest, biomass processing, and evaporative
related losses (Table 4). At a biofuel production level of 10 billion gallons/year in the southwestern
United States, Pate et al. (2011) estimated that algae production would consume 24% percent of all
water used for irrigation in this region. This is a significant concern in the water deficient southwest.
More efficient water recycling, and partnering with waste water streams seem the best way to reduce
some of these requirements. Yang et al. (2011) estimated that as much as 90% of the freshwater usage
could be eliminated by using seawater or waste water sources. Furthermore, thoughtful location, and
cultivation system demand will be critical to reduce the draw and the water supply. Even without taking
this into account, algae water usage is on par with estimates of the water foot print for other biofuel
feedstocks (Table 3). Therefore with respect to water utilization, algae production appears to be the most
environmental favorable option for biofuel production if recycling is part of the process. Still, water and
nutrient recycle likely will be required for any large scale microalgal cultivation operation.
Table 3. Water footprint for microalgae versus other biofuels feedstocks. Adapted from Yang et al. 2011.
Feedstock
Water footprint (kg water/kg biofuel)
Maize
4,015
Sugarcane
3,931
Potatoes
3,748
Soybean
13,676
Switchgrass
2,189
Microalgae
591-3,650
†
†
Range due to variations in recycle rate.
Replacing farm animal feeds
According to UNESCO (2009) total global freshwater use is about 4,000 km
3
/yr. About 70% of this amount
is used in irrigated agriculture (20% goes to industry and energy and 10% for domestic use). Agriculture
also benefits from about 6,400 km
3
of rain water (responsible for about 60% of crop production). A recent
production is appreciated. We predict that from this base of understanding the industry will enter a phase
of steady, if not explosive, growth.
Environmental impacts
Like any other economic activity, algal technology can be expected to have environmental impacts. Large
scale micro-algae cultivation is dependent on water sources (either fresh or salt water), inorganic nutrients
(including nitrogen, phosphorus, iron, potassium, and other trace metals), and CO 2 and energy. In this
section, we will explore the pros and cons of various nutrient and water sources, and how algae compare
to terrestrial sources. For the most part, estimates of water and nutrient usage used here are based on
current algae biomass productivities and lipid content. Improving either of these parameters has direct
effects on improving the environmental and economics of microalgae production. Possible methods for
improving productivity and lipid content will be discussed later in this chapter.
Water
Fresh water footprint
Successful cultivation of algae is dependent on consistent supply of quality water at a predictable cost.
Algae biofuel production is often touted for the fact that they can grow in seawater or brackish water,
and therefore do not have to compete with agricultural uses. While some current algae production does
require fresh water, we will only consider the case of marine algae here, as that is the most pragmatic
approach at commodity scales. However, depending on the cultivation system, and location of production,
there will be significant water demand to compensate for harvest, biomass processing, and evaporative
related losses (Table 4). At a biofuel production level of 10 billion gallons/year in the southwestern
United States, Pate et al. (2011) estimated that algae production would consume 24% percent of all
water used for irrigation in this region. This is a significant concern in the water deficient southwest.
More efficient water recycling, and partnering with waste water streams seem the best way to reduce
some of these requirements. Yang et al. (2011) estimated that as much as 90% of the freshwater usage
could be eliminated by using seawater or waste water sources. Furthermore, thoughtful location, and
cultivation system demand will be critical to reduce the draw and the water supply. Even without taking
this into account, algae water usage is on par with estimates of the water foot print for other biofuel
feedstocks (Table 3). Therefore with respect to water utilization, algae production appears to be the most
environmental favorable option for biofuel production if recycling is part of the process. Still, water and
nutrient recycle likely will be required for any large scale microalgal cultivation operation.
Table 3. Water footprint for microalgae versus other biofuels feedstocks. Adapted from Yang et al. 2011.
Feedstock
Water footprint (kg water/kg biofuel)
Maize
4,015
Sugarcane
3,931
Potatoes
3,748
Soybean
13,676
Switchgrass
2,189
Microalgae
591-3,650
†
†
Range due to variations in recycle rate.
Replacing farm animal feeds
According to UNESCO (2009) total global freshwater use is about 4,000 km
3
/yr. About 70% of this amount
is used in irrigated agriculture (20% goes to industry and energy and 10% for domestic use). Agriculture
also benefits from about 6,400 km
3
of rain water (responsible for about 60% of crop production). A recent