Free-flowing pipes: Detergent lipase to break down kitchen oils

Our project

We set out to tackle a problem that affects almost every kitchen: the build up of fats, oils and grease in pipes. Over time, these deposits cool, solidify and cling to pipe walls, causing blockages and sewage backflows – as well as higher maintenance and operational costs for wastewater systems.

The most common drain-cleaning solutions rely on harsh chemicals like sodium hydroxide and sulfuric acid, which can damage aquatic ecosystems and corrode infrastructure. We wanted to design something safer and more proactive that would prevent fats, oils and grease from becoming a problem in the first place.

Our solution is a process to produce encapsulated lipases that can be added to hand dishwashing detergents. 

These enzymes break down fats, oils and grease during dishwashing, making the fats more soluble in water and reducing the chance they will accumulate in pipes.

Our design solution

We begin by preparing a growth medium of starch, salts and filtered waste oil (which contributes to the sustainability and cost-effectiveness of our process). 

We then inoculate the medium with Chromobacterium viscosum, a bacterium we selected because it produces lipases extracellularly and performs well across a broad range of conditions. This is then transferred to a bioreactor, where the bacteria grow and secrete lipases.

Our mixture then goes through a series of separation and purification steps to reach our target concentration. Cellular waste and unused media are treated and disposed of in municipal wastewater. To make the enzyme robust enough for real-world dishwashing, we immobilize and encapsulate it in a secondary solution that dissolves under typical dishwashing conditions.

Our target production rate is 3,200 tonnes of encapsulated lipase per year.

The technical challenges we faced

We began this capstone project by wanting to address the issue of clogged pipes and originally focused on finding ways to target the problem directly in the pipe. 

We then reframed our problem to address oil and grease before they enter the pipes and become an issue.

One of the largest technical challenges was designing our product so it could work in a range of environments. Lipases are often incorporated into dishwashing pods where they are able to break down fats, oils and grease within a relatively controlled environment with consistent detergent concentrations and known temperatures and cycle durations. Handwashing is more complicated because the conditions are not consistent. Different people wash dishes using different scrubbing techniques, water temperature and amounts of detergent. 

We needed to design our final product formulation so that it would be applicable across a range of conditions.

Equally challenging was figuring out the process once we had created the lipase – everything downstream of that felt like new territory.

What we’re most proud of

This project brought together all of our learning and experiences as undergraduates. 

In the first three years we studied the fundamentals of physics, chemistry and biology in addition to engineering topics on heat transfer and thermodynamics. We didn’t always have a sense of when and where that knowledge would be needed. However, during this capstone project, every one of those parts came into focus and clicked into place.

We are proud we were able to take a broad problem statement and transform it into a concrete, technically sound process with real economic potential.