Food waste – down the bin, drain or in the soil?
I have just discovered a new fact about America. Most American households do not throw their kitchen waste in the garbage bin; they throw it down their drains. An interesting contraption installed under the kitchen sink called the garbage disposal unit captures the food waste, shreds it into small pieces (less than 2mm) after which it passes into the plumbing.
This is in contrast to cities in Asia where most water authorities instruct the people to scrape off all food particles from dishes and throw them in the garbage bin before washing the dishes.
In the US, the rationale behind allowing food waste to become a part of the wastewater circuit is that it is a lesser evil than when it is a part of the solid waste circuit. Carrying food waste in trucks for disposal is fraught with public health and environmental risks, it is believed. If burned in waste-to-energy facilities, the high water content of food scraps does not allow it to generate much energy. If it is buried in landfills, it decomposes to generate methane gas which is a potent greenhouse gas.
On the other hand, when food waste is pulverised with water, the existing sewerage network can be used for transporting it into treatment plants, which are well-equipped to deal with organic solids. These can be converted to biosolids and used as fertilisers for soil. Advanced facilities can also recover methane for producing energy. According to one study, food waste produces three times as much biogas as municipal sewage sludge.
In Asian cities, the case for keeping food waste out of treatment plants is that the higher organic carbon load leads to a higher biological oxygen demand which in turn leads to a higher consumption of oxygen. This increases the cost of aeration. More sludge is produced. Treatment plants in Asia are already struggling to meet the needs of millions and cannot be saddled with the load of food waste. Besides, it also contributes to eutrophication and toxicity of water bodies.
But by far, the best solution even in an urban set-up, which is only being carried out by some environment-conscious individuals is composting at household level. Composting helps to turn food waste into rich soil, which can be used for gardening and farming. Done at household level, it helps to reduce the volume of garbage to be disposed by municipal authorities as well as the load on municipal treatment plants. Also, the release of methane gas from landfills is avoided.
Unfortunately, not much is being done by authorities to disseminate information about composting, and it does not feature as a waste management strategy in most countries. There is a lack of specific targets and economic instruments to drive waste minimisation. The centralised collection of wastes as well as wastewater has become a way of urban life and the authorities are not interested in thinking out of the box. And yet, it has been demonstrated that composting can be done even in apartments.
With food waste forming 10 to 20% of solid wastes in many countries, it is time to take a fresh look at its disposal. Composting is a skill that needs to be taught in schools. Enough waste has been wasted.