Employees operate machine that processes urea granules into pellets at Mwea Rice Growers Multipurpose Society (MRGM) located Mwea, Kirinyaga County. [Nanjinia Wamuswa, Standard]

When Bernard Omondi started rice farming, he thought straws will help him in mulching and improve soil fertility. He was wrong.

“After l harvested and put them back into the field, the straws took long to decompose. In fact, l had difficulties weeding and applying fertiliser,” he tells The Smart Harvest during a visit to his farm in Kano, Kisumu County.

After realising it was not of much use on the farm, Omondi resorted to burning them. But they were increasing after every harvest.

In Mwea, Ngari Muthangati another rice farmer was experiencing the same challenge.

“My six-acre rice farm was producing a lot of straws that kept piling yet were very slow to decompose. They became an eyesore in the paddy fields,” Muthangati says.

Like Muthangati and Omondi, thousands of rice farmers and millers in Western, Nyanza, Mwea, and Eastern have been facing a challenge on how to manage rice straws and husks.

Peter Rachuonyo, production manager at West Kenya Rice Mill, says they produced thousands of tonnes of rice husks in a month but had nowhere to dispose it of. 

“We started burning them after farmers refused to take them because they take too long to decompose,” he says.

But this is no longer the case thanks to a new project dubbed Reduce-Reuse-Recycle Rice Initiative, piloted by Kilimo Trust.

Under the programme, the major rice by-products like husks and straws are converted into useful components of organic manure and reused in rice, tree crops, and horticultural production.

To add value, husks are first carbonated through gasification followed by fortification with extra nutrients. The straws are shredded and undergo vermicomposting (the process by which worms are used to convert organic materials (usually wastes) into a humus-like material known as vermin-compost) resulting in high valued manure for crop use.

Greenhouse gases

Gabriel Olengo, programme assistant at Kilimo Trust says rice processing discharges large amounts of byproducts like husks and straws that if not managed well are detrimental to the ecosystem.

“Rice is one of the crops whose field production activities lead to emissions of large amounts of greenhouse gases like methane and nitrous oxide leading to climatic change and global warming,” he explains.

Olengo says the project focuses on sustainable rice production.

Egerton University is spearheading the vermicomposting programme.

The project lead, Prof Paul Kimurto, from the Faculty of Agriculture at Egerton University says that in rice, out of 100kg, 40 per cent is the grain, and 60 is the straw.

Prof Paul Kimurto says that unlike other cereals like wheat and maize, straw from rice has a lot of silicon and lignin making it hard to degrade.

That is why they are now introducing essential organisms in form of red worms to help biodegrade straws faster into manure.

For vermicomposting, he says that, first, you prepare a chamber and introduce red worms, then add cattle manure with soil in the ratio of one to two (1:2), then put rice straw on top.

“The worms feed and multiply, converting the straws into organic manure,” he explains. Apart from solid manure, worms also produce liquid fertiliser used as both foliar feed and insecticide.

Another technology of recycling is carbonation of husks into biochar used as manure in rice farms. Among carbonators are Mwea Carbonators and Lake Basin Agrotech.

Peter Waweru, the chair of Mwea Carbonators says they have 20 burners that carbonate 200 sacks of biochar every day. They buy each sack of husks for Sh30, after carbonation they sell at Sh200.

“Two sacks of husks make one sack of biochar after carbonation,” says Waweru.

The 10 member-group was trained by Kilimo Trust on business incubation and development.

Michael Mwangi, agronomist with MRGM says they produce 250 metric tonnes of husks annually and the biggest challenge it faced was how to dispose them off.

Today, husks have huge markets from companies and individuals carbonating it into fertilisers.

“The project has turned husks from a menace to useful raw material for fertilisers, now with a huge market. We sell a sack of husks for Sh30, and make some good money out of it,” he says.

Hundreds of farmers are now going for biochar which is both a fertiliser and soil amender for acidity with long curative effects. A bag of 50kg sells between Sh1,000-2,000, compared to commercial fertiliser that costs over Sh2,000.

“The moment l started using biochar in my rice farm for both nursery establishment and field application, l have seen the production increase by at least two bags of rice,” Omondi says.

Mwangi confirms that farmers using biochar and manure from straws experience increased rice production by at least five per cent. 

“There are lots of nutrients in the rice straws and husks because rice crop in its early and mid-vegetative stages imbibes, extracts and translocates these micro and macro elements from the soil and store them in the husks. The silicon that is depleted from our soils can be replenished in the same fields through the application of biochar,” the agronomist explains.

The project also involves the introduction of leguminous crops as the offseason venture after the rice has been harvested from the fields.

“Rotational cropping using legumes that fix nitrogen, adds organic matter to the soil and provides the households with plant proteins plus extra offseason income when the surplus is sold,” says Olengo.