trends and future of sustainable development - TransEco

Another unobvious but existing impact is the risk of other greenhouse gases emission frommicroalgae. At night or on cloudy/rainy day microalgae need to consume oxygen, and this may cause theappearance of anaerobic zone under water surface, which can bring about the emission of CH 4 and N 2 Othat is a 300 times more effective greenhouse gas than CO 2 (Erisman et al., 2009). Furthermore,possible microalgae biomass death caused by toxins, inhibitors, etc. will also result in the emission ofthese greenhouse gases mentioned above.3.2. Economic impactsDespite the higher oil contents in microalgae than other feedstock, such as palm, sunflower, theexpenditures of extracting MBB product (ethanol, biodiesel, biogas, etc.) are even higher. The mostimportant cost is the capital cost which usually happens in the start-up phase. Taking algal biodiesel asexample, capital costs can occupy approximately 49.9% of the total costs (Kovacevic & Wesseler, 2010).As a result, it requires overwhelming investments from bioenergy companies, car industry andgovernments. This will possibly make the MBB uncompetitive and unaffordable, compared to thecurrent price of fossil diesel (about $ 3.4 per gallon in late 2010). Cost data reported in the existingpublications can range from $15 per barrel (Green Car, 2006) to several hundred dollars (Pimentel et al.,2009), depending on climate, species, growing systems and other conditions. Confronted with thissituation, investors will be careful and cautious when they plan to establish a new MBB project now thatthey need to compare and weigh the influences of cost parameters, such as biomass yield, lipid content,capital and operational costs, energy use and other factors.Along with the development of increased automation, labor expenditures will be reduced, but at thesame time more people will be unemployed, and thus workers will suffer from economic pressure. Whatis more, MBB production may compete with the other traditional microalgae usages such as cosmetics,chemicals (Spolaore et al., 2006), which may create the potential depression or shrink in the originalindustries.3.3. Social aspectsThe shortage of trustworthy information including health and safety issues, production transparencyand concerns for the environmental sustainability have been taken as the main key factors in the loss ofconfidence in MBB industry by communities. If chemicals like additives and flocculants are used togather the microalgae and if catalysts and toxic solvents are utilized to extract biofuel, concerns cancome to the anxiety that these substances may residue in co-products and/or byproducts (Krinsky &Johnson, 2005), thus having a detrimental effect on the health of poultry feeding on them. Inevitably,people will also suffer when they are absorbed into our body by chemical accumulation through foodchain. Another public health risk is that the microalgae cultivation system may provide some habitats forlaying and hatching of mosquito eggs and larvae as microalgae are a significant part of their diet(Marten, 2007). These mosquito eggs and larvae can be the main media to transmit diseases, such asmalaria which kills more than 1 million people each year (WHO, 2008). In some cases, concerns havealso been put forth over the potential impacts on the health of field workers.493