Algae Crops: Coproduction of Algae Biofuels - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 363

However, the reality is that the technology is still developing and that poor
management introduces many environmental concerns [ 1 ].
The industry, in its search for best management practices, has developed
approaches that optimize efficiency and create diversification. Conservation, not
dilution, is a solution concept much discussed [ 2 ]. Best management practices
combine aquaculture and hydroponics to integrate fed aquaculture (e.g., fish) with
inorganic and organic extractive aquaculture (e.g., seaweed); thus, the waste of one
system is used as a resource by the other. This type of production system, termed
“aquaponics,” results in a sustainable system with very low-input use, especially for
water. It is a closed system that, in principle, may produce algae, which, in addition
to cleaning the water, can be harvested, sold, and used as an input in production of
industrial products at large scales.
Such sustainable systems suggest great potential. The use of algae to capture
greenhouse gases has been known for many years [ 3 ], as is its potential to sequester
carbon and achieve higher energy productivity than land-based crops. However, the
discussion and the data surrounding algae, and the large technical and economic
barriers faced by producers of algae biofuels, suggest that the use of algae to
produce energy will likely end up being combined with other value-added products
[ 4 ]. The combination of energy production and other coproducts (e.g., wastewater
treatment) can make large-scale algae biofuel production economically viable. Key,
however, to algae biofuel coproduction is the ancillary market's ability to consume
large volumes.
The Economics of Coproduction
The literature discusses the possibilities of coproducing algae biofuel and waste-
water [ 4 ], as well as other high-value algae products. Lundquist et al. [ 4 ] argued that
limited demand for many of the high-value products could restrict the benefits of
these production processes. They argue that large-scale solutions are needed and
conclude that such coproduction systems should be limited to wastewater treatment
and algae biofuels. However, aquaponics might offer an economically viable
alternative to coproduction of wastewater treatment and algae. Future research
will need to show how viable this alternative may be and what are the consequences
of algae being the secondary product—the primary being the fish.
Aquaculture production systems result in water pollution. Because aquaculture
production relies on artificial feed to grow fish, it faces the quandary of increasing
production at the expense of increasing pollution from farm effluent. Because fish
do not consume all artificial food, some food reaches the bottom where it is
decomposed by microorganisms. These residuals can alter the natural food struc-
ture and significantly impact the local environment. Further, fish excretion and fecal
wastes combine with nutrients released from the breakdown of excess feed and may
raise nutrient levels well above normal to result in anoxic conditions. While farmers
can use chemicals to clean the water, the alternative, a sustainable aquaponics