In human history and specifically India’s history, there is a plenty of stigma associated with handling human faeces / shit / poop; whatever you like to call it. I think poop sounds cute. So, I will stick with poop, for the rest of the blog. And pee, for urine.
If handled incorrectly, poop and pee can lead to health and sanitation problems for many. If managed correctly, both can be used as a source of energy and fertilizer. Our current situation is, we are neither here nor there.
We have surely figured out how to build sewage systems for large cities to improve sanitation by quickly distancing our poop from where majority of the population lives. I am not sure about the efficacy of sewage treatment plants though. But if we go by reports or simple observation, we know that most of the waste from our toilets are dumped into ponds, rivers, wells, seas, especially when no one is watching.
Major cities have centralized sewage collection pipelines. But majority of India operates with a decentralized system : every house or a apartment complex has a septic tank. Based on the size of the tank and usage, every few months or years, when the tank gets filled up, a sewage tanker is called to empty the septic tank. The owner of the house pays him for the service and no questions are asked of what is done with the output.
Like the majority of decisions of our lifestyles, we, citizens, have outsourced a critical activity. We keep paying someone so that we don’t have to think about that impact of our actions.
How we got here? Urban agglomerations, and their sewage treatment, in India have mostly aped the west because that’s where we got most of our vision of how we want our civic infrastructure to be. Rural India apes its cities because of the aspirational value they provide in terms of comfort, security and assurance of basic services.
A lot of villages had a system of manual collection of poop which was dumped in a landfill out of the village. ‘Out of sight, out of mind’. This activity was conducted by members of a certain caste and because of the nature of the job, were treated as untouchables.
This practice was an evil system which was needed to be done away with and the centralized sewage system/ decentralized septic tank was an easy solution which could be implemented in a medium term without much behavioural change. While there are now laws to prevent manual scavenging, the profession still exists because technology to clean certain manholes and septic tanks simply don’t exist yet.
We take a valuable resource like freshwater and another valuable resource like poop, mix it together and create a hazardous mix in underground tanks fit for no use. Human ingenuity can be incredulously stupid, no?
While we have come a long way to improve health and sanitation for the majority of the Indian populace, millions are affected by poor hygiene and lack of access to clean drinking water. Groundwater tables are contaminated on account of many reasons, one of which is domestic sewage dumping. India has one of the highest prevalence of water borne diseases in the world. There are multiple ways to deal with poop and pee in which a ignored waste can be converted to a valuable resource instead of being a source of public health obstacle.
बहुत हो गया ज्ञान. Here is what we have done at the farm to deal with poop and pee. While what we have done here is at a very small scale, there already exist solutions to implement these technologies at larger scales. We need to move from linear to circular models in civic infrastructure. I sincerely hope that we as a society move in this direction. Or else, as the saying goes ‘We’re f****d’.
(The asterisks don’t hide an expletive. I wanted to say ‘failed’, what were you thinking? :p)
Urine Diverting Dry Toilet
The most environmental and sanitation friendly way to deal with human poop is to compost it aerobically i.e. in the presence of oxygen. UDDT is also known as Dry Compost Toilet or just Compost Toilet. It is important to separate out the pee from the poop because this is what ensures that the poop compost pile in the composting chambers remains dry and doesn’t produce any stench.
Poop mixing with water is what causes pathogens to flourish and create risks of diseases. Poop is rich in nitrogen; so when it is mixed with a carbon rich materials such as dry leaves, saw dust in the right proportion, it can compost to a rich fertilizer which can be used for non food crops. What is needed for a rich compost which can form humus on the soil, is the right carbon:nitrogen ratio, moisture and oxygen. A good pile will let thermophilic bacteria thrive which will raise the temperature to 60+ degrees Celsius. This temperature ensures that all pathogens including E. Coli get killed.
Pros : Minimum handling of poop. Almost zero smell, definitely less than that of a flush toilet. Very little maintenance. Almost zero water use. Low cost of construction because no excavation needs to be done like that for a septic tank.
Cons : Built off-site; so, difficult for young children and senior citizens to use. Moreover, the one that we have installed is with Indian style commodes and therefore people who are no longer accustomed to squatting will have trouble using it. A dry toilet has space requirement than a conventional flush toilet because two composting chambers need to be constructed for use every alternate year.
Wet toilet flushing to a Biogas plant
Poop mixed with freshwater collected in a septic tank produces methane which is a potent greenhouse gas. Whereas, combustion of methane produces carbon dioxide, which is a less potent greenhouse gas. Biogas plant connected to a sewage collection system is a brilliant use of poop to produce energy from methane and fertilizer from the slurry output. Because of the amount of burgeoning global population, we need to very seriously start considering such technologies, if we want to have any hope of reducing fossil fuel dependence on the Middle East.
We have 3 cows and 4 calves at the farm now. We feed cow dung diluted with water twice every week into the biogas plant. This is in addition to the outlet from the 2 flush toilets directly connected to the plant.
Unfortunately, cows don’t know how to use toilets. If they did, the manual work for feeding the cow dung into the plant will be even lesser.#poorjokealert
The conventional LPG stove has a provision for an air inlet to ensure complete combustion in presence of oxygen. Biogas already consists oxygen. So a minor modification is needed to the stove with either insulation tape or mseal to block the air inlet.
Because anaerobic digestion doesn’t produce heat, it doesn’t eliminate the risk of all pathogens. So it is best to compost biogas slurry aerobically in a hot pile. Every week, once the outlet pits fill up, we transfer the slurry and make aerobic compost piles nearby.
Pros : a Biogas plant can be retrofitted to a flush toilet given there is enough space near the house. Very little behavioural change is needed in use of toilet. Cooking energy is a big bonus. The cost of building a Biogas plant is much lesser compared to a septic tank. Western commodes can be used.
Cons : a lot of behavioural change and space is needed in dealing with the output / slurry, especially if done at a small scale like the farm. Water use is high similar to any conventional toilet. Hot compost piles using biogas slurry need to be turned to make Compost regularly and empty land space
I first encountered a dry compost toilet while volunteering at Sadhana Forest and then AuroOrchard at Auroville, Pondicherry. I got the UDDT compost toilet commodes from EcoPro, Auroville.
The biogas plant was constructed with help from KVIC. They have also offered a subsidy of 50% for the construction of the plant.
I would like to thank people at these communities & organizations, volunteers & masons who constructed the compost toilet and biogas plant for us, for making them a success and hopefully an inspiration for more people.
P. S. Certain certification agencies for organic farmers don’t allow the use of human waste in any form as fertilizer for crops. I am not yet sure of the finer details of this.