How a biogas innovation is providing solutions to air pollution and global warming


A city covered in smoke. PHOTO/PEXELS


For more than 26 years now, Grace Githongo, has been cooking using firewood and charcoal and lighting her house with a kerosene lamp oblivious of the health and environmental implications of her actions.

Household air pollution is regarded as the world’s leading environmental health risk.

According to World Health Organisation (WHO), air pollution causes health complications like strokes, heart diseases, lung cancer, and chronic pulmonary disease (COPD).

WHO says exposure to the smoke produced by fires  kills 4.3 million people each year around the world. Over three billion people use polluting fuels and devices – such as wood, coal and dung in simple stoves – for their daily cooking. The resulting household air pollution is the world’s single greatest environmental health risk.

However, since becoming aware of the dangers of using firewood or charcoal to cook and light her house with a kerosene lamp, Ms Githongo has switched to biogas as her main source of fuel. This is courtesy of a new project called SimGas.

SimGas, a sustainable biogas enterprise from The Netherlands and Kenya aims to reduce air pollution in households and also curb deforestation. SimGas recently won the prestigious international “2018 Climate and Clean Air Award” hosted by the United Nations Environment Programme (UNEP).

The Climate and Clean Air Awards recognize exceptional actions that produce results for the climate, air quality and sustainable development.


SimGas won in the “Innovative Technology” category for their revolutionary, high-quality and affordable biogas systems, which have tremendous positive impact on climate and the health of thousands of farmers in Kenya and Tanzania.

The effects of logging

According to research, firewood or charcoal burning leads to deforestation, which adds more atmospheric CO2 than the sum total of cars and trucks on the world roads and therefore a major contributor to global warming.

The reason that logging is so bad for the climate is that when trees are felled they release the carbon they are storing into the atmosphere, where it mingles with greenhouse gases from other sources and contributes to global warming accordingly.

According to the Environmental Defense Fund (EDF), a leading green group, 32 million acres of tropical rainforest were cut down each year between 2000 and 2009—and the pace of deforestation is still increasing.

In Kenya and Africa in general firewood and charcoal which is used for fueling cooking stoves in most households is a major contributor to deforestation.

Studies shows that Kenya loses Sh 200 billion each year as a result of premature deaths brought about by air pollution, suggesting that dirty air could be killing more people in Kenya than any other health complications.

According to a study by a global policy think tank, The Cost of Air Pollution in Africa authored by, Dr Rana Roy, an average of 19,000 deaths in Kenya arises from air pollution each year.

Dr Roy sums up his report with projections showing that if the pollution problem in Africa is not dealt with, it could become as bad as it is in China in less than three decades.

Air pollution in Africa

A diary farmer in Kenya using SimGas stove to cook in her house. PHOTO/WORLD BANK

“If Africa’s local air pollution is contributing to climate change today, at a time when its population stands at approximately 1.2 billion, or 16 per cent of the world’s population as at 2015, it is safe to suppose that, with unchanged policy settings, it is likely to contribute considerably more when its population increases to approximately 2.5 billion, or 25 per cent of the world’s population in 2050, and thence to approximately 4.4 billion, or 40 per cent of the world’s population in 2100,” Dr Roy says.

One biogas system reduces eight tonnes of CO2 per farmer per year – the equivalent of a person’s eight return flights from Amsterdam to New York City.

World Bank’s Carbon Initiative for Development (Ci-Dev) has an Emissions Reduction Purchase Agreement (ERPA) with SimGas for the purchase of 500,000 Certified Emission Reductions (CERs) – commonly known as carbon credits – generated by SimGas’ biogas systems. With this investment from Ci-Dev, SimGas improves the affordability for rural households to access the self-empowering technology of biogas.

Dairy farmers can use the systems from SimGas to generate their own cooking gas and bio-fertilizer by simply filling the system with cow manure.

While clean cooking systems are not new, SimGas has developed and is selling a truly disruptive technology. The systems are manufactured using plastics and can be transported to remote rural areas more cheaply than traditional masonry-based systems.

With this highly scalable technology and distribution model, SimGas hopes to reach tens of thousands of households in East Africa by 2022 further contributing to the reduction of short-lived climate pollutants.

SimGas was founded in 2009 by brothers Sanne and Mirik Castro. Today more than 2,500 dairy farmers in Kenya and Tanzania make use of SimGas biogas systems.

Household air pollution is largely generated by household fuel combustion, leading to air pollution in and around the home, and contributing to ambient air pollution.


Globally by far the most important direct health risk is pollution caused by the incomplete combustion of fuel in low-efficiency stoves and lamps used for cooking, space heating and lighting.

Research shows that there are other important contributors to household air pollution, which may include radon, emissions from construction and building materials, such as glues or formaldehyde in pressed wood products, flooring or carpets; lead in paint or pipes, asbestos roofing or panels, as well as mould from moisture build up.

According to WHO, household air pollution accounts for 7.7 percent of global mortality. Nearly all of these deaths are in low- and middle-income countries (LMICs), where household air pollution is a leading cause of deaths from noncommunicable diseases.

WHO Director Dr Maria Neira

According to, Dr Maria Neira, WHO Director, for the Department of Public Health, Environmental and Social Determinants of Health, when cities are built using good planning principles, they can also be communities that foster health and well-being.

“Think of the cities or the neighborhoods that you have particularly enjoyed living in or visiting – and how such places looked, felt or even smelt,” she says in a special commentary.

She states that today, more than half of the world’s population lives in cities. By 2050, this proportion is expected to grow to two-thirds.

“People live in cities to be close to employment and educational opportunities and services, and cities can be wonderful places for social interaction and access to cultural activities,” she notes.

Proposed air pollution solutions. IMAGE/WHO

Dr Neira says unfortunately today, many rapidly growing cities are beset with heavy traffic, cramped slums and anonymous high-rise blocks that breed social alienation, noise and violence. All of these have a negative impact on our mental and physical health and well-being.

“One of the best overall “indicators” of a healthy or unhealthy city is air quality. This is because air pollution levels are typically low in well-planned cities with good transport systems, walkable streets and ample green spaces to filter the air,” she notes.

Dr Neira adds that air pollution levels soar in urban settings that prioritize road transport over pedestrians and cyclists, and that allow uncontrolled sprawl in large, grey, unbroken blocs of asphalt and concrete.

“More than 80 percent of all cities worldwide exceed the air quality limits set by the World Health Organization (WHO). And more than half of all cities that monitor air pollution report air quality levels 3.5 times or more than the WHO limits,” she reveals.

Dr Neira observes that air pollution is an insidious killer and every year 3 million people die prematurely due to outdoor air pollution, which is heaviest in major cities of Asia, Africa and Latin America.

“Most of these deaths are due to heart attack, stroke, respiratory diseases and lung cancers – that are also among the world’s top disease killers today,” she says.

Dr Neira shows that when tiny, invisible particles of pollution penetrate deep into people’s lungs and bloodstream, these toxic pollutants accumulate in the body and eventually lead to cardiovascular disease and cancer.

WHO estimates

WHO estimates that air pollution causes about 1 in 3 deaths from stroke, chronic respiratory disease and lung cancer as well as 1 in 4 deaths from heart attack. Ground-level ozone, produced from the interaction of many different pollutants in sunlight, is also a cause of asthma and chronic respiratory illnesses.


“Air pollution is one of the most critical health threats we are facing today. Health and wellbeing must be the number one priority in urban planning. If we don’t take action now, air pollution will choke our cities and make them even more deadly places to live,” she says.

Dr Neira says since most sources of outdoor air pollution are beyond the control of individuals, city mayors and other local leaders need to push for change and commit to tackling air pollution head on.

She adds that local and national governments need to introduce policies and make investments that support cleaner transport, energy-efficient housing, power generation, industry and better municipal waste management.

“But we can also lead change at community and individual level. This can include commitments to cycle or take public transport to work, when safe routes are available; to recycle waste or compost; or conserve water and energy at home and in the office,” says.

Dr Neira says strategies such as “pedibus” initiatives can encourage children to walk to school safely, and the creation of urban gardens can provide both healthy foods and venues for social interaction and physical activity.

Many of these measures to improve environmental health also help people to be more physically active and eat a healthier diet, so reducing obesity and diseases like diabetes and heart disease.

She notes that when cities take action to reduce air pollution, they can achieve dramatic progress adding that almost half of all cities monitoring air pollution in high-income countries reduced air pollution levels by five percent between 2008 and 2013.

“But we must move faster and with more urgency, particularly in low- and middle-income countries where progress on air pollution has not been so encouraging and the air quality is getting worse,” she warns.

Dr Neira adds that cities need to ensure that people know about the levels of air pollution in their city and that they understand its deadly impact on their health. This is the most effective way to trigger action.

WHO has joined forces with United Nations Environment and the Climate Clean Air Coalition on the BreatheLife campaign to give citizens access to this information and to mobilize cities to work together to achieve safe air quality levels by 2030.

Almost 40 cities, including London, Oslo, Santiago, Seoul, Singapore and San Antonio, have joined BreatheLife campaign and the network is continuously expanding.

The SimGas innovation

Officials of SimGas led by Sanne Castro receive the “2018 Climate and Clean Air Award” hosted by the United Nations Environment Programme (UNEP) from, Mr James Shaw, the New Zealand Minister of Climate Change during a ceremony held at the San Francisco Museum of Art. PHOTO/COURTESY

The two brothers behind the SimGas innovation that is helping to tackle the problem of air pollution and global warming in different countries in Africa Sanne and Mirik Castro says their shared passion for socially responsible entrepreneurship and sustainable development inspired them to start SimGas.

Sanne and Mirik Castro founded SimGas BV in 2009, with the idea to design and bring to market a highly scalable biogas digester that would provide clean energy and fertiliser for millions of people.

“The idea arose from my (Sanne) research: In 2008, I visited almost a hundred biogas systems in Ghana and Tanzania, preparing a report for the Dutch Ministry of Foreign Affairs. I was struck by the life-changing experience that happy biogas users had, and at the same time by the sheer amount of units in disrepair,” Sanne said in an online interview.

He continues: “That’s when I started wondering ‘why?’ Why does the same technology work for decades in one house and not at all in another? The main reason was that biogas systems were built by masons one-by-one, making it possible to make mistakes, as well as lacking the scale to provide service.”

Sanne says that soon thereafter, he called his brother Mirik to start a biogas company based on a scalable product and excellent service.

“Mirik, a seasoned entrepreneur, immediately replied ‘yes!’. This is how two brothers with a shared passion for socially responsible entrepreneurship and sustainable development set up a business that would shake things up in the biogas industry,” Sanne adds.

Sanne says that SimGas believes in empowering people by offering them tools that help to improve their lives and income positions.

He adds SimGas biogas systems have great impact on the lives of small scale dairy farmers in East Africa.

“Access to biogas is life changing for rural households: they gain access to 21st century cooking, eliminate the risk of indoor air pollution and have daily access to organic fertilizer to increase their crop yield. With a biogas system dairy farmers become more productive, cost-effective and independent,” he notes.


Sanne adds that currently they have installed 2,500 biogas systems in Kenya and Tanzania, impacting the lives of 12,500 people. He says by 2022 their domestic biogas products will improve the lives of 100,000 people in East Africa.

“Our growth is to be facilitated through our in-house lease financing, remote monitoring and control system in combination with our exclusive agreements with the dairy cooperatives,” he adds.

Studies show that around 3 billion people still cook using solid fuels (such as wood, crop wastes, charcoal, coal and dung) and kerosene in open fires and inefficient stoves. Most of these people are poor, and live in low- and middle-income countries.

These cooking practices are inefficient, and use fuels and technologies that produce high levels of household air pollution with a range of health- damaging pollutants, including small soot particles that penetrate deep into the lungs.

WHO says in poorly ventilated dwellings, indoor smoke can be 100 times higher than acceptable levels for fine particles. Exposure is particularly high among women and young children, who spend the most time near the domestic hearth.

What studies show

WHO says about 3.8 million people a year die prematurely from illness attributable to the household air pollution caused by the inefficient use of solid fuels and kerosene for cooking.

Among these 3.8 million deaths: 27 percent are due to pneumonia, 18 percent from stroke, 27 from ischaemic heart disease, 20 percent from chronic obstructive pulmonary disease (COPD) and 8 percent from lung cancer.

Exposure to household air pollution almost doubles the risk for childhood pneumonia and is responsible for 45 percent of all pneumonia deaths in children less than 5 years old.   

Household air pollution is also risk for acute lower respiratory infections (pneumonia) in adults, and contributes to 28 percent of all adult deaths to pneumonia.

WHO reveals that one in four or 25 percent of premature deaths from chronic obstructive pulmonary disease (COPD) in adults in low- and middle-income countries are due to exposure to household air pollution.

A man stands next to a SimGas biogas digester in Kenya. Biogas digesters decrease pressures on forest resources by lowering demand for wood and charcoal. PHOTO/COURTESY

Women exposed to high levels of indoor smoke are more than two times as likely to suffer from COPD than women who use cleaner fuels and technologies. Among men (who already have a heightened risk of COPD due to their higher rates of smoking), exposure to household air pollution nearly doubles that risk.

Twelve percent of all premature deaths due to stroke can be attributed to the daily exposure to household air pollution arising from cooking with solid fuels and kerosene.

The global health body says approximately 11 percent of all deaths due to ischaemic heart disease, accounting for over a million premature deaths annually, can be attributed to exposure to household air pollution.

WHO adds that approximately 17 percent of premature lung cancer deaths in adults are attributable to exposure to carcinogens from household air pollution caused by cooking with kerosene or solid fuels like wood, charcoal or coal.

The risk for women is higher, due to their role in food preparation.

WHO says more generally, small particulate matter and other pollutants in indoor smoke inflame the airways and lungs, impairing immune response and reducing the oxygen-carrying capacity of the blood.

There is also evidence of links between household air pollution and low birth weight, tuberculosis, cataract, nasopharyngeal and laryngeal cancers.

Air pollution – the silent killer. IMAGE/WHO

Mortality from ischaemic heart disease and stroke are also affected by risk factors such as high blood pressure, unhealthy diet, lack of physical activity and smoking. Some other risks for childhood pneumonia include suboptimal breastfeeding, underweight and second-hand smoke.

For lung cancer and chronic obstructive pulmonary disease, active smoking and second-hand tobacco smoke are also main risk factors.

Impacts on health equity and climate change

WHO says that without a substantial policy change, the total number of people lacking access to clean fuels and technologies will remain largely unchanged by 2030 (International Energy Agency, 2017 (1)) and therefore hinder the achievement of the 2030 Agenda for Sustainable Development.

It says that fuel gathering increases the risk of musculoskeletal damage, consumes considerable time for women and children, limits other productive activities (such as income generation) and takes children away from school. In less secure environments, women and children are at risk of injury and violence during fuel gathering.

Black carbon (sooty particles) and methane emitted by inefficient stove combustion are powerful climate change pollutants.

“Many of the fuels and technologies used by households for cooking, heating and lighting present safety risks. The ingestion of kerosene is the leading cause of childhood poisonings, and a large fraction of the severe burns and injuries occurring in low- and middle-income countries are linked to household energy use for cooking, heating and/or lighting,” WHO says.

The global health body says the lack of access to electricity for 1 billion people (many of whom then use kerosene lamps for lighting) exposes households to very high levels of fine particulate matter.


“The use of polluting lighting fuels introduces other health risks, such as burns, injuries, poisonings, and constrains other opportunities for health and development, like studying or engaging in small crafts and trades, which require adequate lighting,” it adds.

WHO says that it provides technical support to countries in their own evaluations and scale-up of health-promoting household fuels and technologies.

It says that it is building capacity at the country and regional level to address household air pollution through direct consultations and workshops on household energy and health.

It has also issued guidelines for indoor air quality to ensure healthy air in and around the home.

Biogas systems reduce short-lived climate pollutants in homes and adjacent kitchens, and also decrease indoor air pollution – a leading cause of skin, eye, and lung diseases.

SimGas biogas digesters also decrease pressures on forest resources by lowering demand for wood and charcoal used as cooking fuels.

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