Digging the topic - part 3

From here to there

Hi everyone!

The last post I wrote on RE-cycling had interrupted, in a way, the "Digging the Topic" series that I was writing up. Hence, I think it's time to end the trilogy with the last piece of writing. With "Digging the topic - part 3" I will briefly give an overview on all the destinations of waste once collected from our houses, offices and premises. Therefore, following the guideline purpose of my blog, I will be focusing mainly on the MSW (Municipal Solid Waste).

Once collected, the waste starts a journey that ends up somewhere: the waste disposal methods explain in detail this somewhere taking into account all the possible options for the community to get rid of its scraps. Having a look at Figure 1, the Waste Hierarchy described in the newest Defra report “Waste Management in England” helps us to have a better idea of the term "disposal": the bottom of the arrow defines the disposal as an option with no energy recovery while, other disposal methods such as anaerobic digestion, gasification or pyrolysis, are ranked as other recovery because there is a production of reusable energy from their application.

Figure 1: waste hierarchy according to the "Waste Management in England" report (Defra) 

Recycling could be also considered as a disposal method because it is a (great) method to treat the waste. Anyway, we could generically list the disposal methods as follow:

1. Recycling (…and I don’t need to say what recycling is about)

2. Composting. The most complete definition I found out there was provided by Lau et al. in 1991: “controlled biological process which converts biodegradable solid organic matter into a stable humus-like substance” (Lau et al. 1991: 145). Another interesting paper written by Slater and Frederickson (2001), explains what composting means and involves. At this stage of the discussion, what is relevant among the huge amount of information provided is that composting refers mainly to kitchen and garden waste (more widely, it is a biodegradable-waste related method), it is a biological treatment, its output is used as fertilizers in agriculture or in reclamation projects.

3. Anaerobic digestion (AD). I am talking again about organic waste, yet treated in an oxygen-free environment (Alvarez et al. 2000). The outcomes of this technique are very interesting. In 1995, Braber presented a wide overview of the AD advantages, such as the considerable production of energy, reduction of CO₂ emission and, as well as for the composting, less land requirement.

4. Gasification and Pyrolysis. Here, taking a break in citing papers, I found an extremely useful webpage (www.gasification.org) which deals with this disposal methods. Basically, they both consist in burning waste but the former involves high temperature and an aerobic environment while the latter occurs at lower temperatures, it is anaerobic and it uses an indirect source of heat. The most important thing to say is that these methods allow high energy recovery ratios while the simple…

5. …incineration, an aerobic high-temperature waste combustion, often doesn’t. For fully understand the incineration process and its differences with gasification, I think it is time to link the first video.

6. Landfilling, which is the act of placing waste into specific portion of land. All official reports, environmental organization and, above all, the EU, describe landfilling as the last favourite way to treat waste. The reasons are quite straightforward if we consider all the disadvantages that it brings. In 1995, a number of these consequences have been listed by El-Fadel et al. as "gas and leachate generation, […] the migration of gas and leachate away from the landfill and their release into the environment, […] potential health hazards, vegetation damage, […], ground water pollution, air pollution, global warming" (El-Fadel et al. 1995: 1).

Well, the list above wanted to be an overview of the disposal methods together with a brief description of the relative main features. Therefore, concluding “Digging the topic – part 3”, I would say that this post has the double function to explain what the destiny of the rubbish is and, at the same time, to introduce automatically the following discussion: what are pro and cons for each method? In more generic terms, why is this specific sector of waste management so important? Hence, do we have to care about recycling? If yes, why? Looking back at Figure 1, it is clear how Defra wants to make clear that incineration and landfilling are the last favoured option to treat waste. At the same time, RE-RE-RE are at the top of the arrow so it looks like that a clear trail has been blazed. The following posts will be debating the questions above and I will try to understand what responsibility of the masses is within the waste process.

See you soon on RE-cycling!