Biodegradable fraction of MSW should be separated at the household level (to avoid mix with toxic compounds in MSW) and use for anaerobic digestion would be an eco-friendly approach of producing bioenergy. The energy can be recovered in the form of biogas or electricity, and that would somehow contribute to avoidance of the equivalent amount of energy production through the conventional processes (fossil based). Therefore, this approach would contribute for sustainable management of resources.

Dear Ashutosh Kumar,

Terms like 'sustainable' and 'eco-friendly' are of course rather vague and cover a broad range of intentions. In reality, authorities and industries typically look for something that yields a reasonable result, within a certain budget.

Inherently, all waste-processing technologies cost more than the return you can get from them: energy production (and sale) as such is too low (even for MSW incineration). In Europe, a policy-driven waste economy was created to solve this problem, whereby they collect a tax or a contribution from the 'polluters' in order to cover for the outstanding cost associated with the processing of the waste.

Second problem is that recycled products/fractions from mixed waste are of too low quality to be re-used (unless you collect them at the source, before they get mixed up with other waste).Typical problem with bottom ashes from incineration is leachability of heavy metals (for which you must allow maturation of the ashes before you recyle them). Typical problem with digestates from Anaerobic Digestion (AD) is the contamination with non-digestable waste if the biological waste was not source separated. The claimed 'compost'-alike digestate is in fact a threat for public sanity if it would be applied for agricultural use, so this is still the main bottleneck for AD, in Europe and elsewhere in the world. Up to now - whether we like it or not - combustion (incineration) of biowaste as part of a mixed waste is in most cases still the most reliable, 'eco-friendly' and cost-effective method on industrial scale. But once again, one should define which parameters are considered when speaking of 'eco-friendly'. For sure, a biological process is inherently most suited to treat biological waste, but has limitations indeed.

An option could be to make a wet mixture of the waste (=add water to the waste), mix it for some time and then press out the leachate. The leachate stream (containing quite high COD up to 40 g/l) can then we fermented purely wet and the remaining solid part can then be incinerated. This combination offers great advantages for both the incineration process (=avoidance of evaporation loss in the combustion) as well as the AD process (=liquid fermentation is much more easy and effective than solid/liquid fermentation)

kind regards,

Johan

Dear Johan De Greef,

How EU is dealing with resource recovery from their STPs' sludge???

It still remains a problem in many cases, but in general sludge is (co-)combusted, either in MSW-incineration plants (Waste-to-Energy) or in fluidized bed combustors.

Biodegradable fractions of MSW such as inedible animal fats, waste/used frying oils can be converted to fuel grade biodiesel through economical pathways.

Thanx for your contribution Mr. Chakraborty. Could you please share some of your experience in the area of food waste or garden waste especially???

I hva set up more than 50 vermicomposting units in GOA India

where in the food waste/garden waste/canteen waste/agricultural wastes have been successfully treated

Anaerobic digestion process comprises of four major steps...hydrolysis, acidogenesis, acetogenesis and methanogenesis. The biological hydrolysis is the rate limiting step and pretreatment of sludge by chemical, mechanical or thermal disintegration can improve the anaerobic digestion process. Ultrasonic disintegration is a method for breakup of microbial cells to extract intracellular material...

Dear Ashutosh

For some basic insights you may kindly have a look at this article:

Article A review on current status of municipal solid waste manageme...