Poor Grease Management and FOG – the Effects on Wildlife


Two weeks ago, we looked at the environmental impact of poor grease management: how releasing FOGs into our sewers wastes resources and helps to pump greenhouse gases into our atmosphere.

This week, we’ll look more closely at the impact of reckless grease disposal on wildlife.

Beginning with the Smell skunk

We’ve talked about the tendency for uncared-for grease traps to develop a stink before – and we may guess the consequences of this stench on wildlife: a stinking kitchen attracts rats and other pests.

The stench of rancid FOGs in small concentrations in the corner of a kitchen is nothing, however, compared to the stench given off by fatbergs which, gradually forming to block our sewers, trap and hold sewage in place to ferment and decompose.

In short: pouring grease down our drains leads to an almighty stink in our sewers which bolsters the populations of the wrong kind of wildlife and makes infestations of vermin in our homes and businesses much more likely.

Then There’s Sewage Overflow

Fatbergs block our sewers. Blockages make our sewers overflow more regularly: when they do, to avoid raw sewage bubbling up out of our household drains, the sewage is sent straight into our waterways.

Besides filling the water with pathogens – disease-causing bacteria, viruses and parasites – which threaten to infect and kill anything alive in or near the water, sewage also leads to  Bear catching fish in a river suffocation.

That’s because, once in our rivers, the raw sewage decomposes aerobically with the help of bacteria. That means bacteria, breaking down the sewage, use up oxygen dissolved in the water - oxygen which the fish in that water needs to breathe.

Those fish prop up an entire eco-system: small fish are eaten by bigger fish which are in turn eaten by birds and mammals. If the small fish vanish, the creatures that prey on them and the creatures that prey on their predators will all go too.

And that’s not all…

Sewage Overflow Has Subtle Side Effects

Here’s one:

Sewage tends to be rich in phosphates and nitrates - nutrients which promote plant growth.

But this is not as good as it sounds. When an overabundance of phosphorus and nitrogen in fast-flowing river water feeds into stiller water, such as the water of canals, it causes a process called eutrophication.

That means that, during spring and summer, blankets of green algae bloom on the surface of the water. Growing out of control, the algae soak up all the sun’s rays and starve all the other plants in the water.

Then, as summer turns to autumn, the mass of algae dies off and decomposes – again sapping the water of its oxygen and helping to suffocate the critters which rely on that supply.

Pollution spells disaster for the ecosystems which live in our waterways.

river algae

But There Is Hope:

The Thames is a prime example.

Centuries of pollution have left lasting scars on the river’s wildlife: the salmon which once populated the Thames are long gone and invasive species, such as Chinese mitten crabs, now reign supreme where native species once thrived.

But the news is not all bad. Over the years, the Thames has been polluted and cleaned up repeatedly and, each time, much of the wildlife which had fled returned once the water was cleaner.

It happened in the 1850s, when the river, barren of life, harboured cholera and an awful stench. After Parliament commissioned the building of the Victorian sewer system, the river cleared up and small fish such as the sprat soon returned.

It happened again in the 1950s when the river was declared biologically dead. The destruction of the Blitz during the Second World War had meant that, for over a decade, sewage was once again being dumped straight into the river. But, once the sewage system was back up and running, the river began to clear up. By the 1970s, the water was deemed clean enough to attempt to re-introduce the long-lost salmon.

The Wildlife of Our Waterways Can Bounce Back – If We Clean Up Our Act


Stainless steel passive grease trap Stainless Steel Passive Grease Trap 36KGB


Pollution can cause permanent damage to the ecosystems which live in our waterways. But, it’s important to remember that we aren’t struggling in vain.

After a great deal of conservation work to undo centuries of pollution, the Thames is now home to a huge variety of fish and invertebrates which provide food for even more birds and mammals - including 138 seals.

If we take care of how we dispose of our FOGs, we can help to keep it that way.

Do your bit for our river critters – install a grease trap.