The large volume of bio-waste processed by College Group facilities represents a significant percentage of the national throughput. Alternatives to rendering can potentially have the following issues:
On-site burial or landfill
Negative impact on water quality; groundwater contamination; leaching (e.g. chloride, ammonium, nitrate, E. coli); poor biosafety; potential for carcasses to explode from methane build-up (cattle bloat). It can take 25 years for carcasses to decompose.
Releases heavy metals into the air; emits pollutants (e.g. sulphur dioxide, carbon monoxide, nitrogen oxide); airborne toxins can easily reach human food and water supply; poor biosafety.
Accumulation of antibiotics, growth promoters, vaccines, and agricultural chemicals; can concentrate naturally occurring heavy metals; releases CO2 and methane; poor biosafety. Composting bones is very difficult and there are limited uses for the resulting compost.
Leaves large quantities of residual fat; water-intensive process; produces prions and heat-resistant bacteria; seepage; poor biosafety. Digesters work best as a small, local solution, which is generally not logistically or economically viable.