DIY Compost Screeners — Baltimore Community Compost Sites Build Their Own

For Bruno Navarro’s electric, DIY, trommel compost screener, check out this article (Updated March 26, 2024).

As part of ILSR’s Baltimore Composting for Community Project, we are supporting about a dozen community compost sites in the city. This month we hosted two events in Baltimore to build DIY compost screeners designed for the community scale. In collaboration with the Baltimore Office of Sustainability and its Food Matters Project, ILSR partnered with ECO City Farms and ECO’s compost guru, Benny Erez, to adapt and build his two rotating screener (aka trommel screener) designs. One design is people-powered with a simple hand crank. The other has a motor. Both designs rely on repurposed bicycle wheel rims.

Benny Erez at ECO City Farms, Bladensburg, Maryland, demonstrates how his two trommel compost screeners work to Marvin Hayes and Kenny Moss of the Baltimore Compost Collective. The screener on the left is turned with a motor powered by a solar array. The screener on the right is a hand crank. Compost falls through the screener whereas big pieces, aka “overs,” are screened out.

At Granja comunitaria Hidden Harvest, we built the hand crank version for its compost cooperative. At Malcolm House (formerly Jonah House) we built two of the motor-powered design: one for Malcolm House and the other for the Colectivo de Compost de Baltimore.

We secured bicycle wheel rims from multiple local bike shops. Three rims are needed per trommel screener and they all need to be the same size.

One first step was cutting the ¼-inch hardware cloth to size. Members of Hidden Harvest’s composting cooperative cut the hardware cloth.

The bike rims were attached to the hardware cloth temporarily with zip ties later replaced with bolts and nuts.

Strips of wood were secured to inside of each screener to provide not only stability but also to help break up compost during the screening process. Here Marvin Hayes at the Baltimore Compost Collective holds the system for Benny Erez of ECO City Farms.

Left: ILSR’s Sophia Hosain organizes the tools and supplies. She also delivered our new composting site signage to Malcolm House! Right: Sophia saws some lumber to size for the screener frame.

Ausar-Mesh Amen of Malcolm House and Benny make initial adjustments to the rollers.

Why Screen? and Sample Community Composter Screeners

Screening or sifting compost is often worth the effort. It will remove contaminants and pieces of material not fully decomposed (such as wood chips, fruit pits, corn cobs, and pineapple tops). Indeed it is a common step in the community composting process.

There is no one way to screen compost. A common method for home composters is a simple DIY wooden frame around ¼-inch hardware cloth sized to fit over a wheelbarrow. Large-scale industrial sites typically use large rotating “trommel” screeners, which essentially are huge rotating cylinders costing tens of thousands of dollars. Vibrating shaker screeners are also utilized.

Various compost sifters at Earth Matter’s compost demonstration site on Governors’ Island, NYC.

Community-scaled sites have several options, most of which fall into the DIY category. (There generally remains a lack of composting equipment scaled for small-scale sites. Screeners are no exception.) These options include:

Wheelbarrow screener
Table screener
Screener over bin
Standing/folding screener
Rotating or trommel screener (hand crank and electric powered)