Components of the bio-slurry plant and their functions
- Mixing Tank & Inlet pipe: Preparation and introduction of feed stock into the digester.
- Anaerobic Digester: Processing of the raw materials (animal dung).
- Gas piping system: Storage and removal of biogas and by-products from the systems.
- Pressure gauge, biogas stove, lamp and slurry handling structures: Regulation and Utilization of products (gas and bio-slurry).
a) Mixing Tank
- Use adequate quantity of dung daily.
- The inlet to the digester must be blocked during dung mixing.
- Ensure thorough mixing of the animal dung with water and/or urine.
- Let the substrate settle in the tank for a few minutes before charging it into the digester.
- Avoid using water and/or urine contaminated with pesticides.
- Use impurity free substrate (dung/water mixture).
- Dung from slaughter houses should not be used.
- Always leave the mixing chamber clean.
- The mixing should be done daily and always cover the tank after the mixing
.Physical Characteristics of liquid bio-slurry
- Fluidly porridge-like mixture
- Greenish brown in colour
- Odourless (no smell), unlike animal dung slurry
- No foreign materials (maggots, leaves, rubbish etc.)
How to prepare a quality bio-slurry
- Use clean raw materials (dung, water or urine) which are not contaminated with substances like straw and chemicals (acaricides and soap).
- Mix adequate dung according to plant size. Too much dung leads to production of smelly (Semi-digested) bio-slurry and inadequate feeding leads to failure of slurry expulsion from the Expansion chamber and hence production of maggots.
- Use proper mixing ratios (porridge-like mixture). A thick mixture leads to production of smelly
- bio-slurry and a thin mixture lead to low gas production.
Slurry flow canal:
- Should be about 1m (approx. 3ft) long and 25 cm wide.
- Should be sloped to allow easy flow of the slurry out of the expansion chamber and prevent slurry or run-off inflow into the expansion chamber.
Slurry collection pit:
It is a collection point after bio-slurry is expelled from the expansion chamber and a point for the farmer to draw liquid or wet slurry for use as manure or an animal feed supplement.
- Should be 1m long x 1m wide x 0.8m deep.
- Should be covered with a piece of wood or iron sheet to protect the bio-slurry against sunshine and rain water.
- Should be protected against the entry of run-off using either raised soil bank or a
- brick wall.
Slurry composting pits (CP)•
Normally 2 pits (twin pits), which alternate the collection of excess bio-slurry from the slurry during bio-slurry composting. In other words, when one pit is filling with bio-slurry, the second filled pit is undergoing bio-slurry composting.
- The volume of the 2 pits is equivalent to twice the volume of the digester of the biogas plant. Volume= Length x Width x Depth.
- The depth of each CP must not exceed 0.8m (approx. 2.5 ft) to avoid or reduce the risk of having deep pits around the home, for easy turning and scooping out of the mature compost.
COMPOSTING OF LIQUID (WET) BIO-SLURRY.
Conditions required for composting bio-slurry
- Adequate wet and dry organic materials like feed remnants, grass clippings, straw, crop residues, and kitchen waste etc.
- Maintaining optimum amount of water (moisture) by removing excess water.
- Turning the compost pile in order to introduce in air/oxygen (“Aeration”).
- Introducing micro-organisms to decompose the materials (by adding black (loam) soil
- or mature compost).
Procedure for bio-slurry composting
- At the start of the composting process, spread a thick layer of dry materials (15-20 cm) such as litter from leftover of animal feeds, straw, kitchen rubbish and weeds collected from the fields at the bottom of the pit to absorb moisture of the slurry and prevent nutrients from leaching into the ground.
- Let the slurry flow on the dry material so that the latter is soaked with the moisture present in slurry. When it is fully saturated, sprinkle some top soil over it to a thickness of about 5cm.
- Add decomposable materials and some top soil into the pit while it is filling with slurry.
- Composting begins immediately. You may add wood ash if available and this will provide Potassium to the compost.
- When the pit is half filled, the compost should be turned to allow in more air (oxygen) which speeds up the decomposition process. Turning the composting slurry should be done at specified intervals while adding in more decomposable materials and little amounts of soil.
- When the compost is ready, it should be a friable material which can be scooped out of the pit with a spade or hoe and carried to the field using wheelbarrows, sacks, basins or buckets.
- Once in the field, it should be mixed with soil and applied as required or if not used immediately should be heaped and covered properly with
- straw, thin layer of soil or any other
- materials to prevent loss of nutrients through evaporation and leaching due to sunshine or rain respectively.
Note: Sometimes, it may not be possible to complete the decomposition process within the pits especially during cold weather conditions. Therefore, the semi-composted slurry may be removed and heaped in the field under a shade in order to allow complete decomposition. It is not a good idea to heap composted slurry near the bio digester. It should be heaped into the field where it will be applied immediately or sold later.
APPLICATION OF BIO-SLURRY AND USE IN AGRICULTURE.
Bio-slurry for crop production.
In crop production, it is used as quality organic fertilizer (root and foliar) and pesticide for the control of especially insect pests. It can be used to build healthy fertile soils for since it contains readily available plant nutrients (NPK) which contributes to;
- Increased crop yield and improved crop quality.
- Total or partial replacement of chemical fertilizers.
- Decrease in use of artificial pesticides.
Bio-slurry can be applied and utilized on almost all crops which include;
- Fruits such as mangos, oranges and paw paws.
- Maize, sugarcane and rice.
- Fodder such as napier (elephant grass).
Bio-slurry for animal production
Animal enterprises in which bio-slurry is applied and utilized include;
- Pig rearing/piggery
- Local chicken/ Vermi-culture (growing worms) to feed to chicken
- Pisciculture/Fish rearing
Bio-slurry for commercial Production (income generation)
- Bio-slurry is sold as either liquid or composted manure to crop, livestock (piggery and chicken) and fish farmer who do not own biogas plants.
a) Application and utilization in the growing of vegetables (home and kitchen gardening)
Bio-slurry can be applied to vegetables as a natural fertilizer with amazing results. The vegetables include; collards (sukuma wiki), spinach, lettuce, cabbages, onions, egg plants, tomatoes, amaranths family (Green, brown & red varieties), green paper, beans, peas, simsim and mushrooms.
- Dig and prepare a 4ft (wide) x 20ft (long) double dug garden.
- Pour 10-20 litres per m2, liquid bio-slurry, or spread (broadcast) 4,000-8000 kg per acre, bio-slurry compost.
- Plant the vegetable seedlings, observe spacing, then mulch.
2) Growing Plants:
- Mix 1 (bio-slurry): 2(water).
- Filter to remove impurities from the mixture.
- Spray the crops.
- Alternatively, pour the mixture between the crop rows, then mulch.
b) Application and utilization in the growing of coffee
Bio-slurry can be applied to coffee plants just like other organic manures to fertilize the soil and increase coffee yields either directly as liquid (wet) bio-slurry or indirectly as composted bio-slurry.
1) Planting stage
- Dig a 2ft (wide) x 2ft (deep) pit.
- Mix 1 (composted bio-slurry): 1 (black loam soil).
- Plant the coffee seedling at ¾ pit depth.
- Water the seedling, then mulch.
2) Growing stage
- Dig a canal around the plant roots, 2-3 ft from the stem.
- Canal size; 1ft (wide) x 1ft (deep)
- Fill canal with either liquid or bio-slurry compost.
- Cover with soil, then mulch.
3) Control of insect pests (insect repellent)
- Mix 1 (Liquid bio-slurry): 2 (water).
- Filter mixture to remove impurities.
- Spray the mixture onto the crops