July 15, 2019

Stainless Steel Is the Smart Choice for Biodigesters

Durability, good looks, and—most of all—hygiene are why stainless steel is so prevalent in commercial kitchens
By Iain Milnes

Stainless steel is the material of choice for commercial kitchens. From surfaces to utensils to equipment, it is the de-facto standard because it’s easy to clean and can take a beating. This makes it the perfect material for restaurants and other commercial applications. It’s also the material that we use for our commercial-grade equipment: the range of LFC biodigesters and SBT bin tippers.

The reason for this goes beyond its durability and aesthetics; stainless steel has other attributes that make it particularly suitable for the digestion of waste food. But before we discuss that, it’s helpful to understand what distinguishes stainless steel from other metals and alloys.

Just like its cousin carbon steel, stainless steel is an alloy of iron. Unlike iron, which has been in use for over a thousand years, stainless steel is a relative newcomer to the materials science world, having first been produced only 100 years ago. In 1913, Harry Brearley of Sheffield, UK discovered ‘rustless’ steel. Although there had been many prior attempts, Brearley has been credited with inventing the first true stainless steel, which, in his formulation, had a 12.8% chromium content. In fact, after this discovery, Sheffield itself became synonymous with steel and metallurgy.

Today, stainless steel includes about 10-11% chromium. Why chromium? When exposed to air, the chromium in the metal forms a film of chromium oxide over the surface. This film is passive and non-toxic, and most importantly, it prevents the steel from rusting by shielding it from air and moisture. Even if the metal gets scratched, the chromium oxide reforms seamlessly on the surface.

As I mentioned earlier, there’s one more attribute that makes stainless steel ideal for commercial kitchen equipment: its low porosity. Food safety is of utmost concern in a commercial kitchen, so kitchen designers and equipment engineers select non-porous stainless steel because it resists germs and bacteria by preventing them from building up on the surface. Further, the more polished that the stainless steel is, the less porous it is, and therefore the more hygienic it is. Most of the exposed surfaces of our products use “mirror finish” stainless steel. Although this is harder to manufacture than dull stainless steel, it gives the customer a higher quality product.

So stainless steel is much more hygienic than other materials. When we designed the LFC biodigester, we realized that stainless was the only viable material, for several reasons:

  1. Aesthetics: it must integrate well with commercial kitchens (countertops, equipment, appliances).
  2. Low maintenance: it must be easy to keep clean with the same techniques used by kitchen staff to clean other commercial kitchen equipment.
  3. Durability: it must last as long as other appliances and equipment.
  4. When the total life cycle costs are considered, using stainless steel for the entire machine (chassis, drum, and panels) is often the least expensive material option.

The biodigester is usually situated in the kitchen or garde manger area so keeping it clean is essential. However, when you put waste food into the biodigester you will inevitably spill some of the waste on the machine. You need to wipe down the surfaces: in this case, use only fresh water to do so.

The LFC biodigesters from Power Knot have a hose integrated onto the front of the machine that facilitates this cleaning process. And the machines have a Clear Access™ top panel. There are no latches, catches, bumps, holes, or gas struts on the top panel that can trap waste food and make it difficult to keep clean.

Although a customer can expect 20 years of use from one of our products, at the end of life, the stainless steel can easily be recycled compared with a machine that has a chassis made of regular painted steel.

In conclusion, when buying a biodigester for waste food to go into your kitchen, check the quality of the finish on the exposed surfaces and then look “under the hood.” Open the door and see how easy it is to keep clean. Take off one of the side panels to see it the machine is built completely of stainless steel or whether cheaper materials have been used in its construction.