globe, is facing many issues ranging from policy uncertainties, economic barriers,
technical difficulties and logistical challenges in the developing and underdeveloped
countries. The benefit of WtE in developing countries cannot be overemphasised,
despite all the challenges highlighted that are all not clearly defined or understood in
the country. Given that the average heating value of municipal solid waste (MSW) is
approximately 10 MJ/kg, the prospects of utilising MSW as a source of energy
cannot be overemphasised. Recent studies highlighted that, in the United States,
incineration with energy recovery (WtE) from MSW alone reduces the percentage
MSW to about 75% of its annual increase, living only the ash as an issue. However,
huge progress has been reported in utilising this form of ash for different applications
ranging from use as constituent in building and in road constructions [5, 6].
Although several MSW treatment technologies are employed in waste management and disposal across the globe, there is no single treatment technology that can
be used to solve all the problems associated with the MSW. This chapter gives a
comprehensive and detailed highlight of the conventional and advanced waste
treatment technologies for sustainable wastes management giving more emphasis
on hydrothermal waste treatment technology, using supercritical water biomass
gasification (SCWBG) for the treatment of organics, from municipal solid waste
(MSW) at the temperature and pressure of 700
C and 350 bar, respectively.
Supercritical water gasification (SCWG) seems to be the most promising solution
to the increasing percentage of MSW in India. The hydrothermal treatment processes
using supercritical water biomass gasification (SCWG) technology can convert the
organics from MSW which are mainly biomass (food waste, woods, paper and
paperboard, yard trimmings, textiles, etc.) to syngas and other refuse-derived fuels
(RDF).
1.1 Background and Context
Effective MSW is the major challenge of most cities with high population across the
globe because of the heterogeneous nature of the waste and dependence on the
economy of a giving population [7, 8]. However, despite the dependence of waste
generation on the economy of the country, one of the greatest advantages is that the
per capita waste generation in low and middle-income countries generally constitutes a large proportion of organic wastes as indicated in Fig. 1.
It is clear from the figure that, regardless of the economy of a country, biomass or
biodegradable wastes constitute a significant percentage of the generated waste.
Unfortunately, even with the waste management hierarchy, in Fig. 2. which is
designed to curtail landfilling of biodegradable wastes and other fragments of the
MSW, in most countries of the globe including developed countries, a larger
percentage of biodegradable wastes in the MSW directly end up in the landfills. It
is worth remarking that this is a very alarming issue because the decomposition
processes of biodegradable wastes in the landfills always produce methane which is
a greenhouse gas. Starting from this viewpoint, one can notice that municipal solid
Supercritical Water Gasification (SCWG) Technology for Municipal Solid Waste. . .
179
technical difficulties and logistical challenges in the developing and underdeveloped
countries. The benefit of WtE in developing countries cannot be overemphasised,
despite all the challenges highlighted that are all not clearly defined or understood in
the country. Given that the average heating value of municipal solid waste (MSW) is
approximately 10 MJ/kg, the prospects of utilising MSW as a source of energy
cannot be overemphasised. Recent studies highlighted that, in the United States,
incineration with energy recovery (WtE) from MSW alone reduces the percentage
MSW to about 75% of its annual increase, living only the ash as an issue. However,
huge progress has been reported in utilising this form of ash for different applications
ranging from use as constituent in building and in road constructions [5, 6].
Although several MSW treatment technologies are employed in waste management and disposal across the globe, there is no single treatment technology that can
be used to solve all the problems associated with the MSW. This chapter gives a
comprehensive and detailed highlight of the conventional and advanced waste
treatment technologies for sustainable wastes management giving more emphasis
on hydrothermal waste treatment technology, using supercritical water biomass
gasification (SCWBG) for the treatment of organics, from municipal solid waste
(MSW) at the temperature and pressure of 700
C and 350 bar, respectively.
Supercritical water gasification (SCWG) seems to be the most promising solution
to the increasing percentage of MSW in India. The hydrothermal treatment processes
using supercritical water biomass gasification (SCWG) technology can convert the
organics from MSW which are mainly biomass (food waste, woods, paper and
paperboard, yard trimmings, textiles, etc.) to syngas and other refuse-derived fuels
(RDF).
1.1 Background and Context
Effective MSW is the major challenge of most cities with high population across the
globe because of the heterogeneous nature of the waste and dependence on the
economy of a giving population [7, 8]. However, despite the dependence of waste
generation on the economy of the country, one of the greatest advantages is that the
per capita waste generation in low and middle-income countries generally constitutes a large proportion of organic wastes as indicated in Fig. 1.
It is clear from the figure that, regardless of the economy of a country, biomass or
biodegradable wastes constitute a significant percentage of the generated waste.
Unfortunately, even with the waste management hierarchy, in Fig. 2. which is
designed to curtail landfilling of biodegradable wastes and other fragments of the
MSW, in most countries of the globe including developed countries, a larger
percentage of biodegradable wastes in the MSW directly end up in the landfills. It
is worth remarking that this is a very alarming issue because the decomposition
processes of biodegradable wastes in the landfills always produce methane which is
a greenhouse gas. Starting from this viewpoint, one can notice that municipal solid
Supercritical Water Gasification (SCWG) Technology for Municipal Solid Waste. . .
179