Solid Waste Recovery and Processing (Processing Plants)

Objectives Reduction of quantity of wastewater, reduction of BOD value and recovery of solid waste. Solid waste is easier to handle and has more prospects for being recycled. | Objectives Techniques Cost Targeted Livestock System Impact Context of Application Monitoring: EIA, Indicators References

Techniques

Improvement of waste recovery and recycling in slaughterhouses:

- Blood: collection and recycling of blood; indirect heating can reduce the amount of waste water.
- Paunch: dry recovery of paunch content and unusable parts of the paunch for composting and use as fertilizer.
- By-products (heads, lungs, intestines) can be rendered and used.
- Hair and other solid material can be recovered from the wastewater and disposed off as slid waste.
- Tankwater from the rendering process can be evaporated, this will reduce BOD of wastewater but will increase energy requirement.
- Recovery of fat from waste water.
- Dry removal of manure from the animal pens, and protecting the pens from rainwater.
- Aeration of waste water to stimulate the denitrification process.
- Establishment of a rendering plant to process slaughter offal and carcasses. The process should start with sterilization of the material by 130 centigrade for 20 minutes and under pressure of 3 atmosphere. This process is safe for all material except for BSE infected carcasses.

Improvement of waste recovery and recycling from tanneries:

- Reduction of water use will lead to reduction of total waste load and investigate possibilities for recycling water.
- Reduction of the use of salt in the preservation process by better distribution of the salt and adding biodegradable preservatives.
- Hair saving methods are recommended to prevent degraded keratin from entering into the wastewater. Unhairing and liming stages should be separated, both liquids could be recovered and recharged. The hair could be screened out.
- Recovery and re-use of chromium: chromium containing wastewater should be kept separate, chromium can be recovered from this waste water and chromium containing solids. The remainder can be used as source material for glue and animal feedstuff.
- Vegetable tanning can to a large extent replace chromium tanning (e.g. the ‘Liritan’ process in South Africa: a process with a high chemical uptake, low pollution load, uniform penetration of the tan and a shortened process time).

Improvement of waste recovery and recycling in dairy plants:

- Water control practices: closing of water taps and hoses when not in use (make use of automatic shut-off valves).
- Reduction of spillage of milk: pipe-line leaks, valve leaks and pump seals.
- Avoid foam formation in fluid dairy products, since foam will easily run over processing vats etc. ( the use of airtight separators, proper seals on pumps and proper line connections to prevent inflow of air will avoid foam formation).
- Do not discharge buttermilk and whey in the waste water but consider them as useful and valuable products.
- Screening wastewater to recover solids (curd and cheese).

Costs

Costs do depend on the technical package introduced. Costs of many of the technical packages are not very high and result in reduction of losses. Introduction of good management practices requires discipline and qualified and trained personnel.

Targeted Livestock System

Processing industry: slaughterhouses, tanneries and dairy plants

Grazing System

LGA | LGS1 | LGS2 | LGS3 | LGH1 | LGH2 | LGH3 | LGT1 | LGT2 | LGT3
N | N | N | N | N | N | N | N | N | N

Mixed System

MCG | MCR | MCC | MFF | MEF
N | N | N | N | N

Industrial System

IFP | IPL | IPG | IRM | IDU | ISL | ITN | IMP
Y | Y | Y | Y | Y | Y | Y | Y

Impact

- Positive environmental impact

- Reduction of waste load (BOD in waste water)
- Recovery of solid waste for recycling and composting
- Recovery of chromium

- Negative environmental impact

- In some cases: increased use of fossil energy

- Livestock productivity impact

- Increased efficiency of the processing process

Context of Application

- Policy: regulations for the discharge of waste and wastewater from processing industry.

- Institutional: employment of qualified personnel development of good management practices research to develop processing methods with less waste (recovery and recycling) research into the use of by-products.

- Training/education: training of factory personnel in processing techniques and good management practices.

Monitoring : EIA; Indicators

- Quantity of fresh water used per unit of product.
- Recovery rates of material (e.g. fat, chromium, solids) from waste water.
- BOD of waste water per unit of product.
- Qualifications of staff and workers in the processing plant.

References

Verheijen, L.A.H.M., Wiersma, D., Hulshoff Pol, L.W. and de Wit. J. 1996. Management of waste from animal product processing – Livestock and environment, Finding a balance. International Agricultural Centre, Wageningen

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