In-vessel Composter

» Page 1: Introduction

The old way:

The new way:

We think the new way looks better and so far it works better, too.

Some explanation is in order.

The old way is our pile of composting manure and livestock bedding (cornstalks and straw). We raise pigs and rabbits in pens that have to be cleaned regularly. Traditionally we've piled the manure and bedding into a heap, turned it every few weeks with the skid loader, and let it sit. This is a perfectly acceptable form of composting and can achieve high quality results. The only problem is, it can take a year or more to complete, and there is very little ability to control the composting process.

The new way is our in-vessel composter. This form of composting involves putting the manure and bedding into an enclosed vessel of some sort and mixing it every few days until the composting process is complete. We have yet to establish a track record, but according to web research we've done, we could have completed compost in anywhere from a few days to a few weeks. We'll update this page in a few months, after we've put a few batches through it.

Here's what we like so far:

Better temperature control. Today it's about 50 °F outside and sunny. I just took the temperature of our compost heap and it's about 90 °F. Inside the drum, where I have about 1/2 cubic yard of the same stuff, it's about 145 °F. The temperature of compost should be kept above 130 °F for at least three days, which helps to kill insect eggs, parasites, and weed seeds. This increased temperature is produced when the micro-organisms responsible for composting get on with their job. The elevated temperature inside the vessel is also partially due to simple shelter from breezes and from absorption of the sun's radiation.
Better (and easier) mixing. The old method of mixing involves getting on the skid loader and turning the pile. I try to take the pile apart and put what was on the outside on the inside and what was inside, outside. This is an imprecise process at the least, and I only seemed to get around to it every few weeks at best, since turning the heap can't be easily done if it's frozen or a soupy quagmire from rain. The in-vessel composter is driven by a hydraulic motor that runs off the skid loader's hydraulics. Turning the drum involves pulling up next to it with the skid loader, attaching a pair of hydraulic lines, and rotating it for a minute or two. At least in theory ... more on this later.
The ability to take the composter to the work. The composter is built on a frame of steel box beams enabling it to be carried around on the skid loader's pallet forks. We have not yet loaded it up to capacity, so I don't know how easily it can be carried when full, but the potential is there to take it to the pen that needs cleaning, load it there, and then move it back to a standard location for composting.
The ability to put the composter indoors. In really bad weather, it may be necessary to put the composter in the barn. If it's too cold outside for composting in the open, this may be a way we can keep the composting process going year-round. We'll have to experiment with this.

There are a number of published websites with additional information about in-vessel composting, and there are companies that make units for purchase. On the small end of the scale, the ComposTumbler is the most well-known example. On the other end of the scale companies such as Green Mountain Technologies and Wright Environmental Management Inc. supply commercial-scale composting systems. We wanted something in-between these two extremes.

Another example, closer to meeting our needs but still too big and elaborate, was tested at Texas A&M University. Their website lists the following potential benefits of in-vessel composting:

Waste is retained on-farm until composted, eliminating the need to transport raw waste on highways to a centralized composting yard.
Composting can be completed rapidly, resulting in product stabilization/sanitation in 3-6 days.
While in the composter, raw wastes are isolated from the environment until the composting process is complete.
The site manager has precise control of moisture, temperature and aeration during the composting process.
The raw waste loses all offensive odors within 24 hours of composter start-up.
In-vessel composting can maintain a rapid decomposition process year-round regardless of external ambient conditions.
This composting process utilizing separated solids from a freestall barn produces a high quality organic material resembling peat moss.

When we read the Texas A&M article, this sounded like a set of compelling advantages that aligned with our needs. Additionally, we wanted our composter project to adhere to the following parameters:

It needed to be small-farm sized. We raise about 80 feeder pigs a year, along with keeping the breeding stock. Our composter needs to support up to 250 pigs a year. We have not tested the limits with capacity yet, so cannot state whether or not ours is properly sized. Stay tuned.
It needed to be inexpensive and reasonably easy to build for a handy farmer with welding skills.
It needed to be able to be built from commonly available parts, with no custom machining or elaborate electronics.
It needed to be portable.

So, on to how we built it ... Page 2: Design Overview

This project was supported through a Farmer/Rancher grant from Western SARE (Sustainable Agriculture Research and Education). For more information on Western SARE, click on the logo.

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In-vessel Composter