Greenhouse Gas Balance and Algae-Based Biodiesel
This chapter discusses the use of life cycle assessment (LCA) in relation to algal biofuels by first of all describing life cycle assessment (LCA) as a process that considers the whole process chain from biomass production to the biodiesel combustion. The chapter continues with an example in which the methods of life cycle assessment are used to analyse the potential greenhouse gas emissions and energy balance of biodiesel production from microalgae. The design chosen in this study focuses on commercial scale, plastic-bag reactors and the biofixation of CO2 from a nearby power station to assist in the growth of the algae. Eight different scenarios involving photobioreactors are examined that involve two methods for harvesting the algae (mechanical harvesting and chemical harvesting by flocculant); two methods for oil extraction (solvent extraction and high pressure extraction), and also two end-uses for the algal cake that remains after oil extraction (animal feed and production of energy through methane combustion after anaerobic digestion). The scenario results are compared with previous scenarios of biodiesel from microalgae grown in ponds, and also with diesel and canola biodiesel production.
KeywordsLife Cycle Assessment Anaerobic Digestion Carbon Credit High Pressure Extraction Alga Farm
Australian dollars, average value across the 2008–2009 financial year.
Cumulative Energy Demand – method used in life cycle analysis to calculate the total (primary, HHV) energy used.
Methane – a greenhouse gas released naturally during the anaerobic breakdown of organic material, especially in wet environments.
Carbon Dioxide – the primary greenhouse gas.
Carbon Dioxide equivalent units. Indicates the amount of global warming that would result from the introduction of a certain mass of carbon dioxide over a 100 year timescale. Also see GWP.
The Australian Commonwealth Scientific and Industrial Research Organisation.
Greenhouse Gas – a gas which when released to the atmosphere is believed to contribute to global warming and climate change.
Global Warming Potential. A measure of how much a given mass of greenhouse gas contributes to global warming, relative to CO2 (which is by definition 1). Kyoto Protocol values are used in this chapter, i.e. 21 for methane and 310 for nitrous oxide.
hectare.annum – an area of land used for a given purpose over a certain number of years. For example, 10 ha.a could indicate the occupation of 10 ha of land over 1 year, 5 ha over 2 years, etc.
Higher Heating Value – the amount of energy released during fuel combustion once the products have returned to a temperature of 25 °C. This takes into account the latent heat of vaporisation of water.
Intergovernmental Panel on Climate Change.
James Cook University – a public university based in Townsville, Queensland, in Australia.
Life Cycle Assessment – a study of the total impacts from ‘cradle to grave’ resulting from the supply of a given product or service.
Lower Heating Value – as with HHV, but the cooling process is stopped at a temperature of 150 °C, meaning the heat embodied in water vapour is lost. This is typically the case in vehicles, where the water vapour is lost to the atmosphere via the tailpipe.
Nitrous Oxide – a greenhouse gas emitted from the breakdown of animal dung and urine in soil, as well as nitrogen fertilisers in wet environments.
Photobioreactor – a device for growing plants or organisms (especially algae) that admits light, but otherwise operates with a system closed to the environment (no direct exchange of gases or water, generally).
Solar Environmental Tube System – sausage-shaped plastic PBRs used by Victorian company in one of the scenarios examined.
Tonne-Kilometre – a unit to measure the quantity of freight transportation. For example, 20 tkm could indicate 20 t of freight transported 1 km, 10 t transported 2 km, etc.
Ultra Low Sulfur – fuel (generally diesel, ULSD) containing under 50 ppm sulfur.
Wildly optimistic scenario – a scenario where every variable results in the best result possible (in this case, resulting in maximal algal growth).
Extra Low Sulfur – fuel (generally diesel, XLSD) containing under 10 ppm sulphur. In Australia legislation requires diesel fuel to be XLS from 1 January 2009.
- Beer T, Olaru D, Van Der Schoot M, Grant T, Keating B, Hatfield Dodds S, Smith C, Azzi M. Potterton P, Mitchell D, Reynolds Q, Winternitz J, Kierce S, Dickson A, Short,CLT, Heyhoe E (2003) Appropriateness of a 350 million litre biofuels target: report to the Australian Government Department of Industry Tourism and Resources [plus appendices]ITR 2004/001. CSIRO, ABARE, BTRE. 2v, CanberraGoogle Scholar
- Benemann JR (2008) Opportunities and challenges in algae biofuels production: a position paper. http://www.fao.org/uploads/media/algae_positionpaper.pdf
- Benemann JR, Oswald WJ (1996) Systems and economics analysis of microalgae ponds for conversion of CO2 to biomass. Final report to the Department of Energy. Department of Civil Engineering, University of California, BerkeleyGoogle Scholar
- Borowitzka MA, Moheimani NR (2011) Sustainable biofuels from algae. Mitig Adapt Strat Glob Change. doi: 10.1007/s11027-010-9271-9
- Campbell PK, Beer T, Batten D (2009) Greenhouse gas sequestration by algae – energy and greenhouse gas life cycle studies. In: Proceedings of the 6th Australian life-cycle assessment conference. http://conference.alcas.asn.au/2009/Campbell%20Beer%20and%20Batten%20paper.pdf
- Diversified Energy Corporation (2009) Algal biofuels research, development, and commercialization priorities: a commercial economics perspective. Gilbert Available at http://tiny.pl/hxfrc
- Glencross BD (2001) Crop updates – putting a value on lupin use in the aquaculture industry: a fishy business? Department of Agriculture and Food, Western Australia. Available from http://tiny.pl/hxfrd
- Gomez AC, Camacho FG, Grima EM, Merchuk JC (1998) Interaction between CO2-mass transfer, light availability and hydrodynamic stress in the growth of Phaeodactylum tricornutum in a concentric tube airlift photobioreactor. Biotechnol Bioeng 60:318–325Google Scholar
- Gray DMD (2008) Anaerobic digestion of food waste funding opportunity No. EPA-R9-WST-06-004, final report. U.S. Environmental Protection Agency Region 9Google Scholar
- Gutzeit G, Lorch D, Weber A, Engels M, Neis U (2005) Bioflocculent algal-bacterial biomass improves low-cost wastewater treatment. Water Sci Technol 52:9–18Google Scholar
- Horne R, Grant T, Verghese K (2009) Life cycle assessment: principles, practice and prospects. CSIRO Publishing, Collingwood, 175ppGoogle Scholar
- International Standards Organisation (2006) EN ISO 14040:2006 environmental management – life cycle assessment – principles and framework. International Organization for Standards, GenevaGoogle Scholar
- Kadam, KL (2001) Microalgae production from power plant flue gas: environmental implications on a life cycle basis. National Renewable Energy Laboratory, Golden. Technical paper NREL/TP-510-29417Google Scholar
- Mittelbach M, Remschmidt C (2005) Biodiesel: the comprehensive handbook, 2nd edn. Martin Mittelbach, GrazGoogle Scholar
- Mohn FH (1988) Harvesting of micro-algal biomass. In: Borowitzka MA, Borowitzka LJ (eds) Micro-algal biotechnology. Cambridge University Press, Cambridge, pp 395–414Google Scholar
- Molina EG, Fernandez FGA, Camacho FG, Chisti Y (1999) Photobioreactors: light regime, mass transfer and scale up. J Biotechnol 70:233–249Google Scholar
- Posten C (2013) Energy considerations of photobioreactors (Chapter in this volume)Google Scholar
- Sheehan J, Dunahay T, Benemann J, Roessler PA (1998) A look back at the U.S. Department of Energy’s aquatic species program: biodiesel from algae. National Renewable Energy Laboratory. Report NREL/TP-580-24190Google Scholar
- Tredici MR (1999) Photobioreactors. In: Flickinger MC, Drew SW (eds) Encyclopedia of bioprocess technology: fermentation, biocatalysis and bioseparation. Wiley, New York, pp 395–419Google Scholar
- US Department of Energy (2009) National algal biofuels technology roadmap. US Department of Energy Biomass ProgramGoogle Scholar
- Yahi H, Elmaleh S, Coma J (1994) Algal flocculation-sedimentation by pH increase in a continuous reactor. Water Sci Technol 30:259–267Google Scholar