Environmental Engineering Reference
In-Depth Information
of biomass conversion: direct combustion, thermochemical, biochemical, and agrochemical. These
aspects have been described in detail in Rooney et al. (2007).
In 2007, the United States used roughly 542 × 10 9 L of gasoline, approximately one quarter of
the global oil consumption (Vermerris 2008). The United States has been importing more fossil
fuels than it produces within the country (EIA 2011). This dependence on imported oil, combined
with the political instability and ongoing conflicts of the major oil-producing nations has made the
energy crisis a political priority. As a result, the Energy Independence and Security Act (EISA) was
enacted in 2007 to help stimulate biofuel production in the United States. According to the EISA,
by 2022, a minimum of 16 billion gal of cellulosic ethanol per year must be produced (Leistritz
and Hodur 2008). Biofuels will play a major role in the future economics of energy production
(McLaughlin et al. 2011).
Not only will the U.S. economy benefit from an increase in biofuels production, but there are
also large economic benefits that developing countries can gain by joining the biofuel industry.
Conventional biomass products (e.g., wood) are used to provide household energy for people of the
developing world. Here, biomass fuels meet the energy needs of households; however, the combus-
tion of biofuels pollutes the air, causing serious health problems. Reducing these emissions using
improved stoves and better fuels can reduce respiratory illnesses and greenhouse gas emissions
(Kammen 2006). Developing countries would be able to replace a higher percentage of their oil use
because of their smaller consumption level, thus decreasing these emissions. Additionally, the biofuel
industry is labor-intensive and has the potential to create many new jobs. For example, the bioetha-
nol industry offers 4.2 million jobs in Brazil. In the short term, until higher grain prices stimulate a
renewed emphasis on agricultural development, areas that face food shortages or import most of their
food could experience higher food insecurity challenges (Cassman and Liska 2007).
However, bioenergy is not without drawbacks. First-generation biofuels received criticism
because they are produced from food crops. Crops with dual use as food and fuel get rated by their
comparative value as food and biofuel feedstock, leading to an increase in food costs (Cassman and
Liska 2007). For example, corn prices have seen an abrupt increase because of corn's use in ethanol
production. Another criticism is about the replacement of arable land with biofuel crops in place
of food crops, which threatens the sustainability of food production. Other criticisms surrounding
first-generation biofuels include poor water use efficiency of the feedstocks, inability to meet large
volume requirements (except for sugarcane), and the large carbon footprint of ethanol (Fargione
et al. 2008; Searchinger et al. 2008; Stoeglehner and Narodoslawsky 2009; Rathmann et al. 2010).
Because, at the moment, ethanol is only profitable or competitive around $50 per barrel, subsidies
offered by the government play a great role in the expansion of the biofuel market and its increased
production (Ruth 2008).
Second- through fourth-generation biofuels attract less criticism regarding water use efficiency
of the crops and the carbon footprint of the fuel. With the aid of other sources of renewable energy,
problems associated with first-generation biofuels can be reduced in second-generation biofuels.
Using the cellulosic biomass crops of second-generation biofuels instead of food crops of the first
generation would alleviate the food versus fuel competition. Biofuel crops such as sweet sorghum
and jatropha could be grown on marginal lands and contaminated croplands that are deemed unsuit-
able for crop production. This approach will offer the greater environmental benefits of reduced
soil erosion, carbon sequestration, and better utilization of land resources. Former wastelands could
then be used in a profitable way, thus leading to true economic growth and development.
3.2 BIoFuel conversIon
A first-generation biofuel, corn grain, is the most important biomass for bioethanol production
in the United States (~97%) followed by sorghum (2%) and 1% from other crops, beverage/juice
waste, and food processing waste (Nichols and Bothast 2008). Corn and sorghum used for ethanol
Search WWH ::




Custom Search