Sunday, June 16

Day and night soil and its potential usage


Treated water and nutrients are provided for plant growth by pipe irrigation.

LIVING in the 21st century, do we ever think where our daily ablutions end up?

A flush of the WC sends all on its way through urban sewerage and wastewater pipes.

Living in a rural hamlet of six houses and an adjoining primary school and a village shop, we annually pay a fee to our local council for the disposal of our own human waste via septic tanks.

These tanks are cleaned from time to time and thus a maintenance charge is involved for this service. How many readers can remember ‘night soil’ collections?

I first came across the term ‘night soil’ in the mid-1960s when studying at Oxford University.

My college, founded in 1571, in Elizabethan times, was between three streets, one of which was named Ship Street and another was Turl Street.

In Elizabethan times, it is alleged that cleaners would throw the contents of students’ chamber pots through open bedroom windows, aiming for the central open drain in the street below. Innocent passers-by were alerted by the shouts of the cleaners of the offensive effluent coming their way.

In polite parlance, these street names now have debatable origins as to their meanings but in Elizabethan times, more vulgar terms, I suggest, were given to the shouts of the cleaners as they threw students’ excrement towards the central gutter!

Only your imagination may determine what they actually said as they warned the innocent passers-by!

These open street drains were cleaned out at night-time by workers, who took the sewage to a collection point to be transported on heavily laden carts to the outskirts of the city to be sold to farmers for fertiliser for their crops.

Once, in the Asian world, human faeces were taken to padi fields in order to enrich soils of poor nutritional quality. Subsequently, koi carps were introduced to the flooded rice fields, providing both fertiliser and a valuable source of villagers’ protein.

Kuching, Kota Kinabalu and Singapore once experienced their night soil collectors too until it was deemed that both collectors and farmers were susceptible to contracting diseases which could, moreover, be passed up through the food chain via the crops they fertilised.

However, still such practices occur in many parts of our world.


Properties of night soil

Faecal waste contains many useful chemical elements and compounds such as ammonia, phosphorus, potassium and nitrogen which are beneficial to plant growth.

In the 1950’s, night soil collection fell into disrepute as urban populations increased through the post-World War Two baby boom and as more modern sanitation methods were employed.

Undoubtedly, the use of human excreta as a crop fertiliser is a risky business. Today, we can see urban sewage farms and wastewater plants where human sludge can be treated to remove heavy metallic substance with the purified water recycled through our water taps.

Do we really know the sources of the water we drink or shower with daily?


New revolution

Allowing farmers to grow food crops which we purchase from stall-holders, greengrocers and off supermarket shelves, we do not realise that the plants we eat need a regular dosage of phosphorous, potassium, and nitrogen-fixing ingredients in the form of fertilisers.

On a world scale, allowing for the equation input equals output. We dispose of billions of tonnes of human wastage nutrients daily which could be put to effective use in agriculture in providing soils with the necessary growth of plants and animals that we may consume.

A recent study by the University of Illinois’s Department of Civil Environmental Engineering, at Urbana-Champaign, in the US, has analysed 56 cities in the world researching into the feasibility of recycling nitrogen, phosphorous and potassium, back into food production.

The researchers took into account the proximity of agricultural land to the nearest urban community where food crops would be consumed.

Rome was rated as the top city to benefit from human-derived nutrients, whilst the US cities of Boston, Los Angeles and New York proved less effective because of their urban sprawls and the time distance involved in reaching their nearest farming communities.

Cairo could have great potential for if all of its nitrogen resources were utilised, that one city could halve Egypt’s nitrogen fertiliser imports.

On the global scale, these American researchers calculated that Asian cities would be best able to recover nutrients from wastewater, followed by Europe and Africa.

The report frankly declares that further research is needed to take into account nutrient transport distances and further investigations into present re-use strategies.

Thinking aloud, I just wonder how this recycling of human wastage could be turned into fertiliser for our farmers beyond our urban areas in Sarawak and Sabah?

The co-authors of this report emphasise that in some cities, treated water, because of its very weight, is challenging to transport and relatively low in nutrient content.

However, it is possible to produce crystallised fertilisers from human waste.

Waste water that has been treated can be used to both irrigate and fertilise croplands. What a saving this would be to farmers in irrigation costs, using only ‘fresh’ water?

There are various companies around the world which are developing the use of bio-solids from the compounds of human excrement in the form of compost or pellet fertilisers for farmers, especially in East Africa.


A circle of dependence

As all farmers and crop growers will tell us, wherever we happen to be in the world, they have to incur labour, transport, time, and other costs in making their products fit for markets.

Their basic returns are relatively small if they sell to middlemen or supermarket retailers. Yet we buy, for we eat to live and then daily deliver our digested food elsewhere.

This circle could easily be closed if our treated sewage could be properly and safely reconstituted, as at wastewater and sewerage plants, for the benefit of nearby farmers to irrigate or fertilise their crops.

We could then safely eat our farmer’s harvests and redistribute the waste contents of our stomachs back to a recycling process.

In our time of rapid climate change, we still release wastewater and sewage though pipes into rivers and even directly into our seas, thus polluting fish, deprived of oxygen, and allowing algae and slime to grow in rivers in anaerobic profusion.

We swim in the sea and in rivers but how sure are we that we do not contract diseases from those waters? What effect is such urban or local effluent having upon marine life?

Could our human excrement be put to better use and at what cost? These are the disturbing questions we must ask ourselves.

Alongside each wastewater treatment plant and sewerage farm, we need reclamation plants to pipe safe crop water to farmers for irrigation purposes, and treated ‘human excrement conversion factories’ to be established to provide farmers with pellet-form fertilisers.

Every time we flush our lavatories, we should spare a thought as to how our ‘disposals’ could make a better life for us all in the world at large, to include our rivers and oceans.

Technology, if properly applied now, will eliminate any fears of eating fresh fish and vegetables.

Only then can we proudly announce our daily contributions to our food chain now and for further global agricultural production in the years to come.