The benefits and advantages of commercial algal biomass harvesting
Kirsten Heimann, School of Marine and Tropical Biology, and Centre for Sustainable Fisheries and Aquaculture; Centre for Sustainable Fisheries and Aquaculture; and Centre for Biodiscovery and Molecular Development of Therapeutics, James Cook University, Townsville,
and Roger Huerlimann, School of Marine and Tropical Biology, and Centre for Sustainable Fisheries and Aquaculture; Centre for Sustainable Fisheries and Aquaculture, James Cook University, Townsville, Queensland Australia
This chapter outlines the concept of integrated bioremediation and co-product development using microalgae. It ties potential products with taxonomically governed biochemical profiles, which are essential criteria for product-driven strain selection. It closes by briefly describing the current challenges to commercial cultivation and biomass harvesting.
Concept of bioremediation using microalgae with value-adding co-product development
The unprecedented increase in greenhouse gas (GHG) emissions is predicted to lead to rapid environmental changes, such as, for example a general rise in global temperatures, more severe weather conditions and reduced freshwater availability, particularly in countries where freshwater is already a precious resource (Field et al., 2012). Global economies are under increasing pressure by governments and the general public to reduce their carbon emissions. For example, the global carbon dioxide equivalent (CO2e) emissions for 2005 were 44.2 billion tonnes (Herzog, 2009). Many countries have introduced carbon taxes to force industries to rethink and actively work towards carbon reductions of their emissions (Ellis et al., 2010).
Global economies are not only pressured by GHG-induced proposed climate change scenarios, but are further challenged by the prediction of having reached or reaching peak oil and phosphorus in the foreseeable future (most likely in the next 15 years), which will negatively affect industries and agriculture (Cordell et al., 2009; Sorrell et al. 2009). It is possible that appreciable new fossil oil reserves exploration may be possible at greater depths; however, the quality of these so-called heavy oils is poorer, as the oil is more viscous, has a higher sulphur content and, hence, requires additional refining efforts. These efforts will be reflected in increased oil prices. Undeniably though and regardless, fossil oil reserves are not expected to be replenished within acceptable time frames to match the growing energy demands of the future world population (Owen et al., 2010). Peak oil also affects the agricultural sector, as farm machinery is oil driven and pesticides are oil-based products. The application of pesticides have led to sustained food supplies, which is directly linked to population growth (Pfeiffer, 2006). With regards to peak phosphorus, predicted population growth, limited arable land for food production, which is not predicted to increase substantially or in line with estimated population growth (United Nations, 2004), and scarcer freshwater resources as well as more unstable weather conditions and raised temperatures will challenge agriculture and aquaculture industries to meet future nutritional and food supply requirements.
Algae and the oxygenic photosynthetic cyanobacteria (chloroxybactria) offer ideal solutions to the above-mentioned imminent problems, because they can be cultivated year round on non-arable land in various wastewater streams or brackish to marine waters, alleviating the pressure on arable land and freshwater resources. As algae are naturally high in protein and ю-3 polyunsaturated fatty acids and vitamins, which are essential in a balanced diet, they may well become a promising food supplement or food source to ensure a healthy diet for the growing population (Cribb, 2011), most likely not achievable with traditional terrestrial crops. In addition, malnutrition or lack of essential amino acids, fatty acids, minerals, antioxidants and vitamins are linked to numerous diseases, such as nutritional anaemia (iron and B12 deficiency), xerophthalmia (vitamin A deficiency) and endemic goitre (iodine deficiency), which are, according to the World Health Organisation, of growing concern (Edwards, 2010). Many algal strains are also suitable for producing renewable fuels (biodiesel, bioethanol and kerosene), restoring the carbon balance and fertility in weathered soils (biochar) (Bird et al. 2011; 2012), for the bioremediation of carbon dioxide (CO2) (1 DT of biomass remediate 1.83 T of CO2 (McGinn et al., 2011) and nitric oxide containing flue gasses (Nagase et al., 1997) and metal- and nutrient-rich wastewaters (Perales-Vela et al., 2006) (Figure 5.1).
Figure 5.1. Concept of bioremediation using microalgae with value-adding co-product development