Evaluating the potential of municipal solid waste to energy conversion technologies in the Philippines

Municipal solid waste (MSW), which is primarily composed of kitchen and yard wastes, plastics, and paper discarded by households, industries, institutions and commercial establishments, is commonly perceived as a nuisance and a non-valuable material. It usually ends up in uncontrolled dumpsites, especially in poor and developing countries, causing soil and water pollution. Emissions from its degradation contains highly potent greenhouse gases including methane and carbon dioxide. Population growth positively affects MSW generation; hence, more wastes can be expected in the coming years filling up limited areas at a rapid pace. Solid waste management in the Philippines is far from an ideal state considering the rate of waste collection and diversion, varying LGU policies on waste segregation, and limited number of sanitary landfills, which is the preferred method of disposal as stipulated in RA 9003 (Ecological Solid Waste Management). Although, the Philippines has enough land space to accommodate the volume of waste projected for the year 2010 to 2045, siting of landfills for proper disposal of waste may be difficult since most of our land are either forested or agricultural, owned by private entities, or does not meet the specifications for a sanitary landfill. This is enough motivation to find a way to significantly reduce the volume of waste prior to disposal. Thermal conversion technologies including direct combustion, gasification, and pyrolysis can reduce the volume of waste for landfilling by up to 95% while generating energy in the form of heat, electricity, or biofuels. These processes can be operated in a high throughput continuous mode with shorter residence times, which serves as one of its advantages over biochemical processes. With the passing of NSWMC Resolution No. 669 in 2016 (Adopting the Guidelines Governing the Establishment and Operation of Waste to Energy Technologies for Municipal Solid Wastes), conversion of MSW by waste-to-energy (WTE) technologies including thermal conversion methods is now being encouraged in the Philippines. Hence, this lecture primarily aimed to evaluate the potential of converting MSW generated in the Philippines into energy via thermal conversion routes. The composition and characteristics of MSW from the Philippines was primarily evaluated in this lecture to know its suitability as feedstock for thermal conversion processes. MSW from NCR [National Capital Region] and UPLB [University of the Philippines Los Baños] were found to be comparable to that of developed countries with established WTE facilities such as Japan and Europe in terms of heating value, proximate analysis and elemental composition. van Krevelen diagram also indicates the suitability of the Philippine wastes for thermal conversion since it falls within the biomass region. There is no single technology that can solve our problem on solid wastes and combination of different technologies are already being applied in other countries. Among the thermal conversion technologies, direct combustion is the widely used thermal conversion technology to produce heat or electricity and it is considered as the most technologically mature process. However, it is perceived to pose the highest environmental risk due to its emissions which may contain carcinogenic components such as dioxins and furans. In the Philippines, incineration or burning of wastes is currently not permissible as stipulated in Section 20 of RA 8749 (Philippine Clean Air Act). Hence, the future application of MSW direct combustion technologies in the country would greatly depend on scientific and technological evidences that indeed emission control devices or process changes can significantly reduce toxic emissions to allowable levels. Pyrolysis and gasification technologies, on the other hand, are still considered are emerging technologies, nonetheless, these are non-burn methods which are not specifically prohibited by the law to be established in the country. The main products of pyrolysis (char, pyrolytic oil, and syngas) can be considered as alternative fuel sources. Char can also be used in a wide variety of applications including soil enhancement and remediation, wastewater treatment, control of carbon emissions, and animal food production while the liquid product and syngas can be valorized into various chemicals. Gasification, on the other hand, produces syngas as the main product, which can be used for energy generation and high-value chemicals production. The by-product slag or vitrified slag can be used as construction material, aggregates in concrete, or decorative tiles. Pyrolysis and gasification methods are reported to have higher energy conversion potential and lower emissions compared to direct combustion. However, unlike combustion, these technologies are still under development and have not yet reached commercialization. Nonetheless, pyrolysis and gasification technologies are perceived to achieve rapid development in the future.