For tens of thousands of years, human societies have struggled to come up with solutions for what to do with all the waste they produce. It is a dilemma that has grown only more exasperating. Since 2008, according to the United Nations, a majority of the world's population now lives in cities, many of which lack even rudimentary energy generation and waste management infrastructures.
New research findings announced today offer a small, albeit promising, breakthrough in addressing the vexing issue of waste. And the work is taking place at the nexus of rapid urbanization, widening consumer participation and ecological crisis -- that is, in China.
The team of researchers, led by Carol Lin of the City University of Hong Kong, describes successful laboratory testing of a biorefinery procedure that converts stale bakery goods from Starbucks coffee shops into a key consumer goods ingredient. It's a breakthrough that, Lin suggests, could generate a high return on investment and process many tons of garbage that would otherwise end up in a landfill or solid waste incinerator.
"In Hong Kong, the issue of food waste is very important. Each person in Hong Kong produces, on average, a half a kilogram of food waste per day. It's the highest, on average, of all Asian countries," said Lin. She added that three of Hong Kong's landfills will reach capacity by 2018, bringing an already problematic situation to a head.
Refining organic materials is nothing new. Commercial-scale efforts have existed for over a hundred years that convert corn, sugar cane and other plant-based substances into a wide array of products, ranging from fuel such as corn-based ethanol to ingredients in many consumer goods, such as soap and detergents. Henry Ford's original Model T of the early 20th century, for example, was designed to run on hemp-based ethanol.
Since that time, biorefinery techniques have grown in complexity and are now producing chemical substitutes for many petroleum-based materials. Public- and private-sector interest in the process is driven by any number of concerns about fossil fuel supplies, greenhouse gas emissions, generating rural development or scientific research efforts, and building sustainable sources of energy.
It is also potentially profitable. The production of bio-based chemicals could generate, in the estimation of International Energy Agency's task force on biorefinery, $10 billion to $15 billion in revenue for the global chemical industry.
Using food wastes rather than food
What is new about the work of Lin and her colleagues is their success in refining food waste, rather than processing grains that might otherwise be used for food. In this way, their procedure, if expanded to commercial scale, could alleviate stress on municipal waste infrastructures at the same time as producing commercially viable materials that do not constrain food supplies.
"We are developing a new kind of biorefinery, a food biorefinery, and this concept could become very important in the future, as the world strives for greater sustainability," Lin said in a press statement about the research.
"Using corn and other food crops for bio-based fuels and other products may not be sustainable in the long-run. Concerns exist that this approach may increase food prices and contribute to food shortages in some areas of the world. Using waste food as the raw material in a biorefinery certainly would be an effective alternative," she added.
The process works like this: The stale baked goods are mixed with fungi, which generate enzymes that break down the carbohydrates in the food into simple sugars. These are then placed into fermentation tanks, where bacteria convert the sugars to succinic acid.
In 2004, the U.S. Department of Energy identified succinic acid as the leading material that might be converted from biomass to high-value commercial materials. It topped the agency's list of 12 sugar-derived substances.