Lee, Sang-Hyun (Hong-ik University)

Anaerobic Digestion Facility in Urban Area


Food waste is an unavoidable byproduct of human civ-ilization, however it is not always apparent the harm thiswaste has on the earth. Food waste releases methanegas, which when compared with CO2 has 20 times thepotential to heat the earth. There are several ways totreat food waste, but we must choose a method thatdoes not harm the natural environment while being be-neficial to the built environment. One of these methodsis anaerobic digesting which can break down organicwaste into gas, water, and solid sediments. This techno-logy is widely used in rural areas such as farms, but has not been applied to urban areas. Urban sites however, hold great potential to implement this technology as the high density of urban dwellers produce s largeamounts of food waste. In the following research we will see a general overview of anaerobic digestionsystems including methods of installation and the economic benefits of their implementation.

Food Waste

Overall food waste accounts for 13% of waste produced in the UnitedStates. In urban areas this increases to 28% of all commercial waste and 58% of all domestic waste. While paper, a large percentage ofoverall waste, can be disposed of safely through recycling, foodwaste is currently land filled and is directly linked to water, soil, and air contamination.

Expected Benefits

  1. Producing green and renewable energy
  2. Reducing pollution and greenhouse gases
  3. Reducing waste oders and pathogens
  4. Transforming waste into valuable bio-fertilizer

What is Biogas

Biogas is the product of a biological process called anaero-bic digestion. In the absence of oxygen, anaerobic bacte-ria decompose organic matter and produce a gas mainlycomposed of methane (60%) and carbon dioxide, makingit comparable to natural gas. With minor adjustments to equipment this gas can then be used as an energy source for generators, boilers, burners, dryers, or any equipment using propane, gas, or diesel.

Historic of Biogas

The creation of biogas is a natural phenomenon that occursin wetlands, manure stacks, and within the intestines of ani-mals. For centuries, humans have harvested the power of bacteriological digestion, by recovering naturally formed biogas to use in cooking, heating, and engine fuel. In Asia hundre thousands of family digesters were built to pro-vide cooking fuel and lighting in rural areas. During the Se-cond World War, German army trucks were fuelled with bio-gas collected from farmers manure. Over the last 50 years remarkable progress has been made in the development of anaerobic digesters to increase methane yield. Today, hundreds of projects around the world, from small dairy farms that biogas recovery systems are both environmentally and economically sound. In Europe even entirevillages are suppli with electricity and heat from their local centralized biogas plants.

How it works

Anaerobic digestion is a biological process that uses bacteria in an oxygen free environment to convert volatile solids into carbon dioxide, methane, and ammonia. The reaction takes place in an enclosed tankthat may or may not be heated. Currently, anaerobic digestion is the most common method of treatmentused in lge biogas plans, those larger than 5 MGD, due to cost efficiency. There are basically two typesof anaerobic digestion systems, standard rate and high rate. Standard-rate systems are composed of a simple storage tank with sludge added intermittently. The only agitation that occurs comes from the nat-ural mixing caused by gases rising to the surface. Standard-rate operations can be carried out at ambienttemperatures, although heat is sometimes added to speed up biological activity. High-rate systems use acombination of active mixing and carefully controlled elevated temperatures to increase sludge stabili-zation. These systems typically use pre-thickened sewage sludge introduced at a uniform rate to maintainconstant conditions in the reactor.

General Comparison


Energy Content

Chase Plaza Project

Example application of anaerobic digester, I chose here. Before we install this system here, we have to consider these things
a How much food waste will be produced in this food court (Decide tank capacity)

b How can we collect them with out any lose (Collecting method)

c Where to locate collecter and digesters(Inside design)

In this plaza, the estimated people who use this plaza at noon is about 4616(calculated as average).

Suppose that an american eats 1.5lb for a meal and leave 28%. Then we can get 1938.93lb of food waste here and the total power produced for this food waste would be 562.3kw / day. (For food waste 1lb
can produce 0.29kw power)

Like this matter, we can calculate monthly produce and yearly produce of power as well.

Food waste estimation

Tank Capacity

Install Cost

Site Plan Diagram

Sectional Diagram

Energy Compensation


Upper plan is not a real, but just a possibility. The important thing is the change of our concept. I really surprised when I first came in the united states, because food wastes are flowing over in the trash boxes. Of course land size of america is much bigger than my country so disposal could be one of the best way. But we have to know that there is another way that can bring us both money and sustainibility. Just invest your money and time to establish this technology. Food waste free period is comming.

All inclusive PDF

University of califonia(Biogas Tank)

Bio gas stove

Human Gasifire

1 comment:

Anonymous said...

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