‘Zero waste to landfill’ is a common boast (or aspiration), most commonly from large organisations able to benefit from economies of scale with their chosen solutions, coping typically with substantial volumes of homogeneous waste.
But the challenges in achieving this goal for smaller businesses with a wider range of waste types can be far more significant.
The hotel sector is a case in point, with food waste from the restaurant balanced by waste from the rooms across a wide range of organic and non-organic types.
“The digester is all about the dual benefits of making significant cost savings and diverting waste away from landfill.”
Science and engineering company Advetec stepped into this field with its second-generation biothermic digester. In January 2017 one of these was installed at the Best Western Plus Centurion hotel at Midsomer Norton, near Bath.
Since then, it has reduced the volume of the hotel’s waste by a staggering 85%. The installation of the system also inspired general manager Mark Manley to em-brace the goal of zero waste to landfill.
The Advetec continuous feed system takes 72 hours to reduce waste in terms of mass and volume, and can process around 10,000 litres a week.
The systems use a bespoke blend of thermophilic bacteria and bio-stimulants. The digestion process generates an exothermic reaction which, in turn, helps to sustain the bacteria and reduces external energy requirements.
The residue has the calorific value of wood. But although rigid plastics, glass and metal are segregated for recycling, some plastics find their way into the digester.
For the Centurion and other interested hotels, the biothermic digester is all about the dual benefits of making significant cost savings and demonstrating environmental responsibility by diverting waste away from landfill.
At the hotel, use of the digester means that the 4 x 1,100-litre bins which were previously emptied twice a week have been reduced to one per week. The Centurion says it will have made a net saving of more than £4,500 during the year on haulage and disposal costs.
These benefits for hotels, restaurants and other small businesses will improve further as Advetec works on a more compact next-generation system tailored to the specific needs of the hospitality sector.
In 2017, the company launched the next generation of exothermic reactors, the Advetec XO. This refines the bacterial blend, reducing the mass of organic waste by up to 90%. This leaves a dry digestate after 48 to 72 hours.
Both the mechanical integrity and internal processes of the system have been improved, as have the control software and remote monitoring. Among other benefits, this means that the operation can adapt more easily to changing waste profiles at different times.
Specific improvements include a rugged exoskeleton to allow for easier transportation, drive units with increased torque, and a re-design of internal processes determining the flow of waste through the system.
The company has calculated that, together, these enhancements deliver a 10% increase in system efficiency compared with previous models.
Unlike other on-site solutions, Advetec’s exothermic reactors can process non-organic waste mixed in with the organic matter, minimising the need for sorting and separation.
The Advetec XO, which is available in three sizes of between one and 13cu m, can be purchased outright or leased on a managed service agreement. Infrastructure requirements are minimal because it can be set up on any concrete pad of appropriate size with a correct power supply.
‘There’s been a lot of interest in how we’re getting on’
Mark Manley, general manager, Best Western Plus Centurion hotel, Midsomer Norton, said: “All the waste goes through a shredder into the digester and, after that, no intervention is required from hotel staff at all.
“It’s easy to use – you can just forget it’s there.
“If something were to go wrong, Advetec would probably know about it before we did, thanks to remote online cameras mounted outside and inside.
“Once we get to the point of eliminating plastics from the residue, we can use it as a fertiliser on the golf course.
“Within the south-western cluster of hotels, the general managers meet, and there’s been a lot of interest in how we’re getting on with the Advetec system a year in.”
Richard Goff is group chief operating officer at Advetec