Renewable Rather Than Depleting

Material and energy inputs should be renewable rather than depleting

Contributed by Dr. David Shonnard, Robbins Chair and Professor, Department of Chemical Engineering, Director of the Sustainable Futures Institute, Michigan Technological University, Houghton, MI USA

The Earth contains finite resources to support sustainable development into the future (unless mankind invents methods to import enormous quantities of raw materials from off the planet-not likely in the near term). As the human population on Earth increases to a projected peak of 9-10 billion from its current level of 7 billion by 2100 and as standards of living rise for many in developing countries, ever increasing pressure will be exerted on finite resources. As increased demand meets an ever-shrinking resource supply, prices for commodity materials and energy will rise. Evidence of this is already happening for petroleum whose current price of approximately $100/barrel is roughly 2.5 times higher than the average from 1987-2000 of $40/barrel (expressed in constant U.S. dollars). There are environmental costs as well to continued reliance on non-renewable raw materials, for example environmental degradation like open pit mines, waste piles, and climate warming by release of CO2 from combustion of fossil fuels (petroleum fuels, natural gas, and coal).

Developing a Bio-Based Economy

Renewable materials and energy can help address some of these negative effects. As noted in the discussion of Green Chemistry Principle #7 by Dr. Richard Wool, the photosynthetic production of biomass from the Earth’s land base is many more times the required amount to provide for all human material and energy needs through a bio-based economy. To utilize these renewable raw materials, innovations in Green Chemistry and Engineering are needed. Research in academia, government, and the private sector is making progress toward commercial production of advanced biofuels and other products, as the following examples show. Pyrolysis and catalytic hydrotreatment can produce hydrocarbon fuels from biomass or municipal solid waste in a matter of seconds rather than millions of years required by nature to accomplish the same result. The use of wood in buildings leads to removal of CO2 from the atmosphere and storage of carbon in stable forms for many decades, thereby helping mitigate effects of climate warming. High production volume chemicals such as ethylene are being produced commercially using sugarcane ethanol as a raw material. Regenerated cellulose fabric is being obtained from hardwood raw materials using an organic solvent spinning process for use in clothing and other fabrics. Solar, wind, hydro, and geothermal electricity sources are low emitters of greenhouse gases (GHGs) and their use in chemical manufacturing can lower the GHG intensity of the chemical industry.

While research is leading to innovative new processes and products based on renewable feedstocks, chemicals and fuels obtained from them may not always be more sustainable than identical products derived from fossil resources, and therefore caution must be used when renewable feedstocks are employed. For example, indigo extracted from plant materials is much more energy intensive than when obtained through a synthetic organic chemistry route (Shonnard et al. 2003). Biofuels derived from energy crops grown on agricultural lands that may displace food production have the potential (if not properly managed) to emit more CO2than the savings relative to petroleum fuels (Searchinger et al., 2008). These lessons demonstrate that prior to introducing chemicals, plastics, or other products derived from renewable feedstocks into the market on a large scale a comprehensive “cradle-to-grave” environmental sustainability assessment should be conducted. This will assure that the new products have advantages environmentally and socio-economically compared to conventional products.

• Searchinger T, Heimlich R, Houghton RA, Dong F, Elobeid A, Fabiosa J, Tokgoz S, Hayes D, Yu TH (2008) Use of U.S. croplands for biofuels increases greenhouse gases through emissions from land-use change. Science. DOI: 10.1126/science.1151861; 10.1126/science.1151861
• Shonnard, D.R., Kicherer, A., and Saling, P., 2003, Industrial Applications Using BASF Eco-Efficiency Analysis: Perspectives on Green Engineering Principles, Environmental Science and Technology, 37(23), 5340-5348.
• *Anastas, P.T., and Zimmerman, J.B., "Design through the Twelve Principles of Green Engineering", Env. Sci. and Tech., 37, 5, 94A-101A, 200

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