Mr Lambly took the Chronicle through the rendering plant process.
In peak season the plant processes 250 tonnes of product a day. It needs 10 staff then, and works 18 hours a day.
The product - animal parts otherwise unsaleable, including heads and hocks - is from Imlay and Land Meat in Wanganui and from meatworks owned by Affco in Manawatu. At peak times 40 per cent comes from outside Wanganui. The animal parts arrive in trucks and are tipped into a holding hopper next to the plant. Once there it is difficult to get them out. From the hopper they are moved up a conveyor belt into the plant building.
They are heated - essentially cooked - at 120C. Then they are screened. The solids are ground, dried and ground again to make meat and bone meal. The liquid, tallow, is squeezed out.
The meat and bone meal goes into pet food and animal feeds, and can also be used as a garden fertiliser. The tallow is used in other foodstuffs, and also as a fuel and in cosmetics.
Air from the plant is filtered through a bed of bark and soil, in an effort to remove odours.
The rendering process was moved into a stand-alone building at Imlay during the 2004-6 redevelopment. The equipment used was already old at that time. It is now more than 25 years old and Mr Lambly said it needed replacing - hence the upgrade.
There's a new element being added - the wastewater from the rendering process is getting an extra stage of treatment.
It's going into a new evaporator in a silver tower beside the rendering building. Most of the heat used in the rendering process up to that point has been provided by gas. The evaporator reuses some of that heat for the new process, and retains it in a vacuum.
Heating the wastewater boils off the liquid and concentrates any solids left. They are removed, to become part of meat and bone meal.
"It allows us to recover those solids and put them straight back into the dryer," Mr Lambly said.
The new evaporator will halve the amount of solids from the rendering process entering Wanganui's wastewater treatment system. Its biological oxygen demand - the nutrients that grow algae - will be reduced, and so will its solids.