Bio-slurry discharged from the reactor retains all nutrients originally present in the feeding material which makes bio-slurry a potent organic fertilizer. Proper application has been proven to provide higher yields than regular manure. It also provides a viable solution to nutrient depletion of many agricultural soils in developing countries. The nutritional value of the slurry can greatly be improved if urine can also be collected in the digester. The use of bio-slurry thus considerably boosts agri- and horticultural production and will improve productivity of fish rearing.
What is bio-slurry?
The mixture of dung and water which enters the biogas plant in semi liquid form is called “undigested slurry.” The undigested slurry undergoes a series of anaerobic digestion processes or fermentation in a biogas digester and is converted into combustible gas called “biogas.” The residue of the fermentation comes out as sludge which is known as “digested bio-slurry.”
Composition of bio-slurry
The composition of bio-slurry depends on the feeding and the amount of water added to the dung. When the dung is mixed with equal amounts of water, after digestion the composition of slurry is recorded as: water 93% and dry matter 7%. The Nitrogen (N), Phosphorus (P) and Potassium (K) are the most required nutrients to the plants. NPK content in liquid slurry is 0.25%, 0.13% and 0.12% respectively.
Characteristics of digested bio-slurry
1. Being fully fermented, bio-slurry is odorless and does not attract flies.
2. Bio-slurry repels termites and pests that are attracted to raw dung.
3. Bio-slurry reduces weed growth. Application of bio-slurry has proved to reduce weed growth by up to 50%.
4. Bio-slurry is an excellent soil conditioner, adds humus, and enhances the soil’s capacity to retain water.
5. Bio-slurry is pathogen-free. The fermentation of dung in the reactor kills organisms causing plant disease.
Proper utilization of bio-slurry
1. All major plant nutrients (such as NPK) are preserved during fermentation process so that plants can immediately absorb these nutrients. It can also be applied as ready-to-use manure.
2. After being stored for a few days or mixed in a 1:1 composition with water, bio-slurry can be applied directly to vegetables or fruit crops around the household. Bio-slurry application along with installation of regular irrigation channels is beneficial for the growth of vegetables especially root vegetables, paddy, sugarcane, fruit trees, and nursery saplings. Mushroom cultivations also benefits greatly from bio-slurry application.
3. Spraying bio-slurry (with or without a little addition of pesticide) can effectively control red spiders and aphids attacking vegetables, wheat and cotton. The effect of bio-slurry with 15- 20% pesticide in pest-control is proven to produce the same results asusing pure pesticides.
4. Dressing of barley seeds with bio-slurry is an extremely effective way to control the barley yellow mosaic virus, which is one of the most destructive diseases in barley growing areas.
5. Dried digested slurry has great potential to be used as feed supplement for cattle, pigs, poultry, and fish.
BIRU advocates bio-slurry application as organic fertilizer that supports nutrient cycles as well as checks soil degradation and erosion. In addition to that, the biogas process is carbon neutral, thus contributing to the global reduction of greenhouse gas emissions for better care of Mother Nature. Utilizing bio-slurry is the next step towards turning waste into benefits.