Sidebar 1. How Much Ethanol Could the Municipal Solid Waste from a City With One Million People Produce?
The average person in the United States generates approximately 1.8 kilograms of municipal solid waste (MSW) every day. Of this, typically about 75 percent is predominantly cellulosic organic material, including waste paper, wood wastes, cardboard, and waste food scraps. Thus, a city with 1 million people produces around 1,800 tonnes of MSW in total, or about 1,300 tonnes per day of organic material.
Using technology that could convert organic waste to ethanol, roughly 330 liters of ethanol could be produced per tonne of organic waste. Thus, 1,300 tonnes per day of organic waste from a city with 1 million people would be enough feedstock to produce about 430,000 liters of ethanol per day, or approximately 150 million liters per year. This is enough fuel to meet the needs of more than 58,000 people in the United States; 360,000 people in France; or nearly 2.6 million people in China at current rates of per capita fuel use.
Source: Jim Easterly, Easterly Consulting, personal communication with Peter Stair, Worldwatch Institute, March 2006.
Estimates of the longer-term potential for harnessing biomass energy range widely and depend on factors such as the extent to which the yields of both food and energy crops can increase, the size of the human population, and the per capita human demand for food and land. Theoretically, biomass supplies could be huge, rivaling current oil supplies.
Over the next two decades, existing starch, sugar, and oilseed crop varieties will continue to provide the bulk of the biomass supplies used for biofuel production. Biofuels grown in tropical areas are cheaper and can displace a larger share of petroleum than biofuels produced with more temperate feedstock. European countries will likely find it preferable to import biofuels rather than attempt to grow all of their own. The United States may be able to produce more indigenous biofuel, but will ultimately face similar limitations.
Since the next-generation conversion technologies are on the verge of viability, continued research and development could be helpful. But extensive deployment is perhaps more important. This will allow operators to streamline new facilities while also reducing the risk perceived by investors looking at an “unproven” technology.
Key Economic and Social Issues, including Agriculture and Rural Development
Petroleum is a highly concentrated energy resource, and the world’s current transportation systems are almost completely dependent on it. As a result, the world economy is (or could be) at risk if oil supplies are disrupted in any of the relatively few countries that are significant oil exporters. As a result of concentrated wealth, social tensions, and inadequate political institutions, many of these countries are less-than-secure suppliers of the world’s most vital commodity. Biofuels promise to bring a much broader group of countries into the liquid fuel business, diversifying