Vermi Composting

Introduction

This project set out to design and build a large-scale vermicomposting bin for use at the school, with the aim of providing a practical and sustainable solution to the food waste produced on campus every day. Vermicomposting is the process of using worms, typically red wigglers, to break down organic waste into a rich, nutrient-dense fertiliser known as vermicast or worm castings, along with a liquid byproduct called leachate that can be used as a liquid plant feed. Rather than sending food waste to a landfill, the bin converts it into something directly useful, closing the loop between waste and resource in a way that is visible and educational for students. The finished bin measures 2.4 metres in length, 1.2 metres in width, and 0.6 metres in height, giving it enough capacity to process a meaningful volume of food waste on a continuous basis. The project sits within the school's STEM programme and was designed, built, and documented by students, covering practical skills in fabrication, welding, and materials, as well as the biological and environmental principles behind composting. From the first ideas on paper through to the complications encountered during the build, this document tracks how the project evolved, the decisions that were made along the way, and what the finished system will mean for the school going forward.

Problem Solutions

Use

The vermicomposting bin will be a genuine asset to the school once it is up and running. The original concept had been to simply use a bathtub as the composting vessel, but the limitations of that idea became obvious fairly quickly, a bathtub has no real capacity to handle the volume of food waste a school produces, and it offers no control over the process. This bin is built to a scale that can actually make a dent in the school's food waste output, turning it into usable fertiliser rather than sending it to landfill. It also integrates well into the school environment without being a burden to maintain. Even during school holidays, this won't be an issue, there are always staff and other people on campus, so the worms will continue to be looked after and the system kept running without relying on the academic calendar. It is a low-maintenance, long-term solution that serves both a practical environmental purpose and gives students a hands-on connection to sustainability.

Materials

The original plan was to take a pre-built frame we had found on campus and build upward from there, attaching walls to the existing structure to form the bin. It seemed like the most straightforward approach at the time: work with what was already there and save ourselves the effort of constructing something from scratch. As the project progressed, however, it became clear that this wasn't going to be practical. The pre-built frame turned out to be low-grade metal, and when we attempted to weld onto it, the heat was creating holes rather than solid joins, which made it unusable as a base. From there, we rethought the whole structure and decided it would actually be simpler and more reliable to build an inner frame ourselves. Metal rods were welded together to form a support structure sitting halfway up inside the bin, designed to hold the plastic sheets that would make up the walls. Angle line was then used as a sleeve or channel along the edges, gripping the sheets in place and keeping everything secure. The final material list came to eight plastic sheets, an angle line for the wall holders, and the welded metal rod inner frame.

Obstacles

The build came with its fair share of complications along the way. Materials took longer to arrive than expected, which pushed the timeline back and meant some decisions had to be made on the fly once things finally came in. The plastic sheets we had originally planned to use were far too thick; they would have required an excessive amount of plastic to work with, driven up costs significantly, and made the whole bin much heavier than it needed to be, so we moved to thinner sheets instead. That change also meant the larger angle line we had sourced for the original sheets was now too big, and we had to switch to a smaller size that suited the thinner material better. Even with the adjusted sheets, we found we didn't have quite enough to complete the walls and had to get additional plastic and melt it down to fill the gaps. Looking ahead, another challenge that still needs to be addressed is the mechanism for moving the finished compost through and out of the bin, a motor or auger system will need to be designed and built to do this properly, since the material won't move on its own at this scale.

Sketches

Idea

Putting a wood block was the first idea, we then switched to full plastic sheets and angle line

Measurements

Based on the pre built frame, these are lengths and widths needed

Dimentions

eight plastic sheets were needed to fill the spaces

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