Page 31 - Energy from Toxic Organic Waste for Heat and Power Generation

Energy Extraction From Toxic Waste Originating From Food Processing Industries 19

microbes, certain microbes like Kluyveromyces can directly utilize lactose
in whey to produce ethanol. Potato processing wastewater results from dif-
ferent operations. Silt water is a result of washing raw potatoes, while pro-
cessing water results from peeling, cutting, cooking, grinding, and packing
[2, 11]. Potato processing wastewater is rich in starch, which theoretically
makes a good substrate for alcohol production. Tomato waste is one of the
most produced and least explored types of waste. The majority of tomato
pomace produced is used in animal feed, and its application in fuel pro-
duction is not well-studied. An average of 40% of the weight of processed
tomatoes ends as waste and is obtained after pressing of fresh tomatoes; and,
typically contains 33% seeds, 27% skin, and 40% pulp [2, 12]. In addition,
dried tomato pomace contains fermentable simple sugars like fructose, glu-
cose, and sucrose [2, 13].
Apple pomace is produced as a result of apple processing and includes
peel, core, seed, calyx, stem, and soft tissues [12]. Commercial technologies
are becoming effective in reducing the amount of pomace produced; how-
ever, 12%–20% of the original weight of processed apples end up as pomace
produced by the juice industry [2, 14]. Grape pomace is the solid residue
that remains after juice extraction or wine production from grapes [2, 15].
Typically, pomaces are composted, processed into animal feed, or used in the
extraction of oil from seeds. Though many of these wastes have some degree
of utilization, not all are utilized to their full potential. Therefore, using these
wastes in alcohol production could be a promising option.

3.3 FOOD WASTE AND ITS ASSOCIATED PROBLEM

It is challenging to estimate the amount of food waste and its global variabil-
ity; as discussed above, available data often do not permit strict calculation
of food waste. Available evidence suggests that food loss and waste represent
a considerable portion of the global food supply, roughly one-third of the
food produced globally by weight, or one of every four kilocalories pro-
duced [1, 16]. Silvennoinen et al. [17] and Betz et al. [18] found that, in the
Finnish food service system, around 20% of food served is wasted just in the
processes of preparation and handling. In Switzerland, an estimation shows
that food storage, food preparation, and food serving losses, combined with
plate waste, in total is around 18% of total food grown.
In the United States, food waste generation is estimated at approximately
0.28 kg/person/day or approximately 31% by weight of food available at
retail and consumer levels. This food waste estimate may be conservative,