The fate of our household waste

What happens to our garbage after collection ?
Interesting question in more ways than one. Firstly, because this garbage is potentially rich. Secondly, because they are poorly treated, they can become very dangerous for the environment and for men. A few years ago, when piles of garbage littered the arteries of our cities, the issue fed the columns of the press through various projects to transform this waste. It was said that there was enormous wealth that only needed to be exploited.

What is waste treatment? What processing methods can we rationally use? With what results?
These are some of the questions that can allow us to stay in the problem of the future of our waste.

1. Incineration

It is a technique that consists of incinerating or burning waste at high temperature. To be applied, certain conditions must be met. As a priority, the calorific value of the waste to be incinerated must be sufficiently high. In other words, this garbage must be able to burn easily. This is a necessary but not essential condition in that it is always technically possible to incinerate waste with a very low calorific value, i.e. very wet waste. However, this is precisely the case for our waste, which contains about 90% organic matter and is therefore very humid. They therefore burn very badly. To get an idea, remember to burn rotten vegetables or tuber peels. To be able to burn such waste, it is either necessary to dry it or to bring an amount of energy of any kind to facilitate combustion. This combustion emits toxic fumes that must be treated before release to the atmosphere. The cost of this operation naturally becomes expensive: installation of incinerators, fuel amendment, treatment of toxic fumes released, etc. It is essentially at this level that lies the difficulty of this mode of treatment.

In both cases, this solution is not economically viable. So where does it come from that this mode of treatment is practiced abundantly in the West, would you say? There are several reasons for this. First of all, Western waste, unlike ours, is very rich in cellulosic materials. In other words, they burn very well. In addition, the incineration process collects heat that can be used to warm households during the winter seasons, and thus amortize the cost of treatment. This is not conceivable in tropical areas. Some have proposed to produce electric current from these incinerators. But once again, the question arises. In a country with enormous potential in terms of hydroelectric dams, can the cost of electrical energy produced by garbage incineration be competitive.... But on the other hand, because of the high pollution it generates, incineration is down sharply in Western countries. Hold on, for example! The Belfort Incineration Plant was closed a few years ago because of the intolerable amounts of dioxin it released into the wild.

Popular in the 1960s and 1970s, incineration is now giving way to recycling. It is now used only for extremely dangerous hospital waste. Where does it come from when we want to import otherwise expensive techniques here and everywhere else in sharp decline? The question indeed deserves to be asked at a time when African countries are becoming gigantic "garbage cans" where extraordinary products are dumped in the West.

2. Recycling

Let's say it from the outset, this is certainly the way of processing the future. It is a process by which waste management has as its priority its recovery. The objective is to take advantage of waste in the form of energy and/or material, which is then considered a secondary raw material in the sense that its non-zero economic value can be exploited. In this sense, waste is considered to be a bearer of wealth.

Like incineration, recycling requires certain conditions to be met, including curbside recycling, economic fabric and secondary raw materials. Recycling increases the costs of managing (collection, sorting and transport) waste, which must be offset by the resale of the quality finished product. In addition, it involves the participation of many actors who must demonstrate the same will: political and administrative authorities, waste producers, recycling companies and potential consumers of recycled products. In concrete terms, households must be able to have several types of garbage cans to sort waste at the source if you want to have a good quality recycled product.

In our country, it is a revolution in mentalities that should be carried out so that every inhabitant of our major cities has at least three garbage cans when we know that at the moment, few households have only one. However, this should be achieved. The second problem is that of the quantities of raw materials. Our waste, as we have pointed out, contains about 90% organic matter. Therefore, the product that can be made in quantity from this waste is compost, since the percentage of other types of household waste collected cannot justify the installation of recycling units. An artisanal revaluation is nevertheless made of bottles, plastic, iron, copper...

3. Composting

It is a recycling technique that consists of a controlled transformation (fermentation in the presence of oxygen) of organic matter that produces an organic amendment that can be used on farms. It deserves special treatment in our remarks because it could indeed be very interesting for farmers and because it has also been the subject of much controversy.

The use of this technique also requires prerequisites. To have quality compost, waste would first have to be sorted. It was accepted that this sorting could be done from the households or mechanically at the composting site. But this mechanical sorting is only operational to purify solid waste such as iron, glass, cans, etc. However, there are all kinds of waste in bins, including liquid waste, or even hazardous hospital waste that can soil biodegradable waste. A compost made from this waste would therefore be extremely toxic. For example, the heavy metals contained in this waste will end up in the compost and in the food it will be used to produce. Quality compost can therefore only be made if people manage to sort waste from the household. This is not a sinecure. But, that's not all, you still have to be able to sell this compost. Because it is not enough to be able to do it technically for it to be feasible and profitable. In the city of Yaoundé alone, about 700t of household waste is currently collected per day. Technically, 150 to 200t of compost can be derived daily.

It is necessary to be able to sell this tonnage to make the production unit profitable. It should be noted that compost in an intensive agriculture context does not replace fertilizers (NPK type). It is only an organic amendment. The question is therefore who can consume 200t of compost per day in the vicinity of Yaoundé. It is also important to know that compost produced and transported over more than 50-75km round entails a cost that, by affecting the selling price, no longer allows us to compete with chemical fertilizers. It goes without saying that the choice of farmers will be made all the faster the quantity/yield ratio is thanks to fertilizers. But at a time when organic farming is clearly increasing, we can indeed think that the trend could reverse and that we would find ways to raise awareness of curbside recycling and planters about organic farming. This is probably the future.

4. Controlled landfill.

But in the meantime, controlled landfilling continues to be used. It is a technique that simply consists in facilitating the biodegradability of the household waste collected by compacting it, and placing it in successive layers in the bowls moved for this purpose. This is by far the least expensive method of treatment. It is at the root of all other treatment methods. Because whatever the technique, we are always faced with ultimate residues that must be landfilled. The conditions are less draconian: favorable geographical location (at least 200m from the houses); sufficient soil tightness (so that leachates do not infiltrate and contaminate the water table) and availability of covering materials, especially the land.

This mode of treatment is also declining sharply in Western countries where there are serious space problems. But for our countries, given the financial means, the nature of the waste, it is currently the most rational method of treatment, provided that we respect the levels of waste quality control, that the various effluents, in particular leachates and biogas, are treated before releasing them into the wild.

In conclusion, the fate of waste is a product that must be understood by the implementation of a global policy that includes the association of the different types of treatment according to the type of waste considered: compost for biodegradable waste, incineration for hospital waste, recycling for plastic and glass, recovery for used tires, landfilling for other types of waste as well as ultimate waste.