Biogas Potential from Slums in São Paulo

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1		Camila Agner D'Aquino	--	1723	2022-06-27 16:01:19	\|
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This entry is adapted from the peer-reviewed paper 10.3390/su14127016

Slums are populated poor areas inside urban centers, mostly deprived of good-quality public services and exposed to inappropriate waste disposal and energy poverty. Using the organic fraction waste from these communities to generate high value-added products, including electricity, heat, and fertilizer, provides a circular bioeconomy with mitigation of greenhouse gas emissions, reducing environmental pollution and diseases.

renewable energy source biogas urban waste bioelectricity waste-to-energy

1. Introduction

Slums are densely populated housing settlements without previous urbanization planning, usually associated with poverty. The houses are predominantly self-built and with a high degree of precariousness by low-income families in a situation of vulnerability ^[1]. As the emergence of the slums is associated with income concentration and unemployment in Brazil, the condition of vulnerability present in these communities is intrinsic to the UN concept of poverty ^[2]^[3]. Energy poverty is one of the manifestations of poverty, defined through the situation in which a house cannot meet the basic energy supply needs due to insufficient income ^[2].

Among the problems, the population faces living in these settlements include high rates of violence, deficient or absent water, sanitation, and electricity network services, low access to public transportation, low access to education, lack of cultural spaces and events, and fewer job opportunities opportunity. In addition, water and soil quality are affected by inappropriate disposal of waste at open dumping grounds, negatively impacting human health. Studies have shown that poor waste management is correlated with higher rates of diseases such as pneumonia, typhoid fever, lung infection, and bloody diarrhea. Also, dumpsites show a high concentration of heavy metals, like mercury, cadmium, arsenic, lead, and chromium, correlated with neurotoxic and carcinogenic effects ^[4].

Adequate waste management is based on the principles of sustainable development, considering its potential as a resource and its impact on public health ^[5]. Considering the high costs of waste collection and disposal, the destination of waste to energy production can reduce air, water, and land pollution and possible illnesses and deaths. Biogas is related to the best waste to energy (WtE) technology to treat the organic wastes from the available existing paths. It is a compact route and has various products range (biogas, electricity, biomethane, organic fertilizer), besides being carbon neutral ^[6].

The infrastructure for collection and disposal of the solid waste generated in the municipality, called Municipal Solid Waste (MSW), is especially lacking in areas such as slums due to its high costs for the local government ^[4]^[7]. A decentralized approach producing biogas from the Organic Fraction of Municipal Solid Waste (OFMSW) has been demonstrated as an affordable initiative to reduce costs and GHGs emissions, and to maximize both the integration of the produced energy into the regional matrix and the use of the end products, as the biofertilizer, for the local community ^[8]. Therefore, local community participation has been a positive factor in the project’s affordability, requiring lower resources for operation and maintenance and encouraging source segregation, resulting in increased recycling ^[9]^[10].

The Brazilian electricity scenario faces the challenge of recovering its renewable mix while reducing costs and improving reliability in the face of recent episodes of high risk of shortages due to poor planning, deficiencies in the system’s operation, and expansion capacity, combined with skyrocketing costs and tariffs. Brazil is uniquely endowed with renewable energy resources, mainly hydro, wind, solar, and biomass. However, over the last two decades, with the hiring of new capacity and the dispatch of the available capacity mix, thermal power has increased its share in supply, negatively impacting costs and emissions. Increasing non-dispatchable sources, like solar and wind, may expand renewable sources and reduce costs. However, the absence of storage structures reduces their contribution to the electric system. Biogas is a decentralized and flexible source that can be operated based on demand, allowing for dispatchable operation due to storage capacity, as herein proposed, can play a similar role in enhancing the value of PV solar resources ^[11].

Moreover, in vulnerable areas, such as slums, decentralized energy facilities, such as biogas and solar, can work as infrastructure hubs, reducing the local energy supply costs and as virtual power plants to the local energy grid ^[12]. So, energy mix diversification focused on the WTE perspective can be strategic to improve energy system reliability, enhance urban sustainability, reduce costs with waste management and energy distribution, promote access to sanitation, and improve communities’ quality of life and health in vulnerable situations.

Additionally, the Brazilian electricity scenario faces the challenge of keeping its renewable matrix composition for the following years but mitigating the hydrological risk. The increase of non-dispatchable sources, like solar and wind, promises this clean expansion. Still, the absence of storage structures reduces their contribution to the electric system, resulting in the dependence of thermal power plants to meet demand with high-reliability levels ^[11].

2. Waste Management in the Municipality of São Paulo

In 2014, the São Paulo government launched the Integrated Solid Waste Management Plan for the City of São Paulo (PGIRS-SP), intending to improve solid waste management based on: non-generation, reduction, reuse, recycling, and correctly treating and disposal of solid waste. The plan includes the maximum waste segregation and its valuation and is applied to all public and private agents responsible for waste management.

The MSW collection and transportation is divided into two regions and is operated by two different private companies. The collected MSW is disposed of in the two operating landfills: East Waste Treatment Plan (CTL) landfill and the Environmental Treatment and Valorization Center (CTVA) Caieiras landfill ^[13]^[14], which receive daily 7000 and 10,625 tons of waste, respectively. Annually, São Paulo generates around 3.8 million tons of MSW, from which only 50 thousand goes to recycling. The remaining waste goes to landfill disposal and it is composed mainly by organic waste (49%), plastic (15%), paper and cardboard (11%) and diapers (11%) ^[15].

At the same time, the options for the correct destination of this waste are increasingly limited. Since the existing sanitary landfills are reaching their limit, both landfills must be closed until 2026, and there is no available land to construct new landfills. So, different approaches to waste management are important to be understood to face the new scenario. According to ^[16], an integrated waste solution for São Paulo city using the biological treatment of OFMSW to produce electricity and compost and a route to promote sorting technologies to recycle materials can reduce 70% of the material sent to landfills and impacts while promoting the highest social impact, compared with other options.

Currently, there are no large-scale biogas plants in the city of São Paulo. There is only the Experimental Unit in the urban area, located in the Institute of Energy and Environment, with an installed capacity of 75 kWe that can receive around 20 tons/day of kitchen and gardening waste. Nearby, all the large landfills use landfill gas to produce electricity. For example, Caieiras landfill has an installed capacity of 29.5 MW, located 40 km from São Paulo, and CTL landfill, of 5 MW, located 30 km from São Paulo. In the whole State of São Paulo, there are 60 operational biogas plants, 16 of them large-scale units and mostly from the sanitation sector (75%).

3. Electricity Consumption, Social Impact, and Biogas Relevance in the Context

Access to electricity can impact access to goods and services like education, food, heating, cooling, light, technology, and others, and it is considered in many ways a human right ^[17]. The main impact caused by the lack of access to electricity is the social inequality since only an adequate supply of energy can provide the conditions to eradicate poverty, improving the well-being of people in social and economic vulnerability ^[3]. The difference in energy consumption between countries is a great indicator of economic, cultural, and social development. Developed countries consume almost three times the world’s annual per capita average of 85 GJ, while poor countries can present values 10 times lower than the global average ^[18]. The same differences can be seen on a regional scale, where families with high social vulnerability consume less energy and are in a condition of energy poverty. In contrast, families with social and economic privileges have better access to electricity. However, improving the electricity access to these communities results in higher electricity demand for the whole electric system, besides new investments in infrastructure to produce and distribute, which can impact the electricity cost to society, including low-income consumers.

Distributed Energy Systems (DESs), as micro-cogeneration and local energy hubs, can be advantageous in demand-side management ^[19]. In this case, biogas has a positive impact because of its flexibility and relatively cheap energy storage compared to other technologies. The latest studies have indicated that biogas in MSW-based biogas-solar-wind systems costs 22% less over the project’s lifetime as they are less dependent on changes in fuel price due to locally available substrates ^[19]. In addition to these aspects, studies indicate that biogas also has a positive impact on CO₂ mitigation, the reduction of waste mismanagement, and the balance of stochastic energy production from intermittent renewable energy sources. Hybrid energy storage systems are more efficient and more economically attractive due to the possibility of interleaving between storage models, in which biogas can be used for long-term storage. At the same time, batteries can attend to short-term demand, resulting in maximum efficiency and an economically viable system ^[20]^[21]^[22]^[23]. Furthermore, the storage of compressed biogas in a biogas-solar-wind scheme can offset the energy fluctuations of different REs outputs and reduce the costs of battery energy storage ^[23]. Furthermore, the installation of biogas plants in these communities, as community-based microgrid (CBMG) or to inject electricity into the national grid, can also generate about 0.775–1.05 new local jobs per GWh, being one-third correlated to the development and implementation of the facilities, and two-thirds related to the operation ^[24].

This concept can have a particular impact on vulnerable communities, providing “immediate resilience” in the project, a higher domain, and a more secure return on investment ^[25]. According to the study by von Wirth, Gislason, and Seidl (2018), the success of a new renewable energy installation should consider not only the technical-economic feasibility but also the general approval, the local context, and the engagement of collective actors and individuals, to promote a connection between the community need and the technology solutions ^[19]. So, biogas-based DES can be a local solution for waste management, energy access, and CO₂ mitigation, with the proper engagement of multiple stakeholders, with economic and social impacts, such as job generation and postponement of investments in the electric energy distribution and transmission sectors, focusing on technical quality, economic viability, and social ethic.

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Subjects: Area Studies

Contributors MDPI registered users' name will be linked to their SciProfiles pages. To register with us, please refer to https://encyclopedia.pub/register :

Camila Agner D’Aquino

Bruno Alves Pereira

Tulio Sawatani

Samantha Moura Coelho

Alice Tagima

Julia Ferrarese Borba

Samantha Santos

Ildo Luis Sauer

Camila D'Aquino

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Entry Collection: Environmental Sciences

Update Date: 28 Jun 2022

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1. Introduction

2. Waste Management in the Municipality of São Paulo

3. Electricity Consumption, Social Impact, and Biogas Relevance in the Context

References