The literature on the use of onsite food waste for medium sized restoration using an in-vessel composter technology is limited. A summary report by the EPA (Henry and Bergeron, 2005) on compost used in forest land restoration has no example of smaller localized food waste compost mixtures. However, there is strong evidence that the addition of organic matter (of any origin) improves permeability and porosity; cation exchange diversity, buffers pH changes, and changes density of soil. Composting improves the physical soil characteristics and soil stability is influenced by aggregate formation to allow for percolation into the ground and can bind or degrade heavy metal pollutants (Brady and Weil, 2000, Singer and Munns, 2002). Most of these studies used large commercial offsite composters or waste treatment compost that take significantly more time to compost. The literature also suggests that increase microbial diversity from the compost will help promote seedling growth (Bonnette, J., and R.E. Green, 1995). Extrapolating from the use of compost from commercial biowaste units, we concluded that food waste diversion provides a safe method for onsite soil amendments that can be used in reforestation (Platt, Ross, and Poland, 2012).
The smaller in-vessel units are not common in restoration efforts. Most compost mixtures from these types of units are used in organic gardening. We wanted to have a unit that we can control the type of compost that we create including carbon to nitrogen ratio, texture, and microfauna. We installed an in-vessel composter in September, 2012 at the Masonic Home site and have been producing compost with a 2 month turn around for use in reforestation. Green Mountain Technologies has developed “The Earth Flow” which is an in-vessel system that converts up to two tons of weekly organic waste into compost. Shredded woody, green waste and horse manure are added to the system so decomposition will produce rich compost ready to be used in restoration within 2-4 months. The design incorporates a fully enclosed vessel and odor control system with an inclined auger for mixing, shredding, and discharging the organic waste. The typical process time for the waste to flow through the vessel is 14 to 21 days which is then monitored in piles before spreading and planting.
Using the proven mixing technology of the inclined auger, the Earth Flow automates auger movement to create one of the most sophisticated in-vessel composting systems on the market. The Earth Flow is capable of composting between 300 lbs and 3000 lbs per day of biodegradables (depending upon system size). The Earth Flow system excels at producing compost of superior quality. The auger mixes, breaks up, and aerates the compost producing an extremely friable (e.g., light and fluffy) mix. Oxygenating compost creates a rich environment for beneficial microorganisms which break down the material quickly.
The design of the Earth flow uses “Plug flow” which means that raw waste is added into one end of the vessel and compost comes out the other end. In the process, the auger also moves the compost slowly toward the discharge end of the vessel. Once materials arrive at the discharge end, the hot composting phase is complete and the material is ready to be discharged from the system.
We are reforesting the area with live oak plant series (about 30 different species of native trees, shrubs, and flowers). We are using compost from food waste, horse manure, and landscape waste. In theory the compost will enrich depleted soil to sustain native trees, shrubs, and flowers. This long term (10-20 years) conservation activity will restore soil, plant communities, and increase habitat for native wildlife.
We currently are planting 3-7 year old plants. We are also planting in areas where cattle still roam, but putting added protection around the plants or seeds. Funds from this project are from Tri-Ced Recycling and Masonic Home. Plants and seeds are coming from Tule Ponds at Tyson Lagoon and California Historical Park, where the Math Science Nucleus maintains small nurseries. The establishment of trees will reduce the carbon imprint while improving habitat for birds (including raptors like the golden eagle, kites, and other large birds) and native mammals, amphibians and reptiles that have survived the urbanization of the San Francisco Bay.
Volunteers learn how to safely compost food waste using a combination of in-vessel composting and creating piles that will be used for keeping the trees with nutrients. A program that is well managed will allow the compost to be used effectively. This will prevent trees and shrubs from dying. We project that the food waste can be used onsite for 10-20 years. The visibility of this program will also allow other areas that could be reforested in the immediate area. East Bay Regional Park with its thousands of acres surrounds this site.