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Agrilab Technologies: Gaelan Brown

Moneek February 21, 2014


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Special Guest: Gaelan Brown

Author/Expert

Composting to Recover Heat, Build Soil and Grow Food

What is Compost Heat Recovery?

Agrilab Technologies: Gaelan Brown

Heat recovery from composting was practiced anecdotally in China 2000 years ago by placing garbage between greenhouse growing beds to generate heat. In the 1970’s French Farmer Jean Pain promoted the practice of coiling pipes through decomposing wood chips to heat water. The New Alchemy Institute did further research and demonstration using active compost and heat recovery in the 1970’s and 1980’s.

Compost is natural recycling – converting food scraps, leaves, manures into soil building compost and mulch. During the decomposition process, medium and large compost piles generate substantial heat. The biological process releases energy visible as steam.We capture the steam/vapor generated during the composting process (125-165ºF) and channel it through an insulated network. An efficient electric fan, or fans on a timer, control the vacuum of the compost vapor. It is drawn into a controlled chamber which houses 6-12 Isobar® tubes – two-phase super conductors which transfer the heat from the vapor. A portion of the Isobars® are sealed into a water tank.

When the water temperature in the pre-heater reaches the desired temperature, it can then be directly circulated to where it is needed. The heated water could also be transferred into larger hot water reservoirs for direct use or circulated for specific heating needs. The only moving parts are the small in-line blower fan(s) and a required circulator pump for the heated water. Both are commonly available and easily replaced if necessary.

Our patented Isobar technology facilitates capturing the heat generated during the composting process. This heat can then be used for numerous applications ranging from space heating of buildings, greenhouses, aquaculture, or hot water and facilities needs. Farms, composters and waste management companies currently use propane, oil and diesel for the bulk of their energy needs. Heat capture and transfer can play a valuable role in offsetting dependence and expenses related to the use of these traditional fuels.

Containerized Isobar Unit (CIU)

Agrilab Technologies LLC, AGT’s Isobar® system actively aerates composting materials to eliminate the need for mechanical “turning” of the feedstock, reducing the cost of compost production. The patented Isobar® heat-exchange tubes capture thermal energy from the compost to create large reliable volumes of hot water (110-130 degrees F) for use in space-heating, winter greenhouses, radiant floors, or process heat for wash water and sterilization. AGT has several successful systems in operation on farms and compost facilities in VT, NH and NY including at Jasper Hill Creamery and the University of New Hampshire. The new Containerized Isobar® Unit (CIU) makes the system mobile and easy to deploy with any existing compost-production operation.

The CIU is housed in a standard 40’ shipping container and is designed to produce 80,000 to 200,000 Btu/hr continuously depending on the amount of compost being produced. This can result in $35,000 to $70,000 per year in potential energy + compost value with operations that have 5 to 10 cubic yards of average daily compost feedstock volume.

Vapor from active compost piles is drawn into ductwork from a series of pipes aligned with bays, or windrows of active compost. The number of intake pipes corresponds to the number of compost bays and can be managed by shut- off valves. The intake pipes consolidate into one pipe which connects to the Isobar® Unit (CIU).
How does it work?
​AGT’s unique approach pulls heated vapor from the bottom of an aerated compost pile or an in-vessel composting system. In most cases, infloor aeration channels are set into an insulated concrete slab to enable negative aeration (suction). The aerated concrete slab makes it possible to produce compost on a commercial scale without regular batch turning because the system actively aerates the material throughout the process.
Mixed manure, bedding, separated solids, or other biomass are loaded on the composting floor on top of a layer of wood chips. The wood chips promote air distribution at the base of the compost. The CIU is designed for a minimum of 5 cubic yards of average daily feedstock volume.

Vapor from active compost piles is drawn into ductwork from a series of pipes aligned with bays, or windrows of active compost. The number of intake pipes corresponds to the number of compost bays and can be managed by shut- off valves. The intake pipes consolidate into one pipe which connects to the Isobar® Unit (CIU).

Vapor from hot compost is pulled into the Isobar® Heat Recovery Unit vapor duct. Shown here is a system installed in a utility room. In the CIU, this ductwork and all of the heat exchange and control systems are inside the 40 foot container. The CIU also houses an integrated control system which monitors vapor temperatures and operating conditions. This data can be monitored remotely and recorded to track trends in temperature.

The Isobar® heat transfer tubes extend through the vapor duct and into a primary exchange water tank, where the thermal energy is transferred to heated water. The heated water can be pumped to reservoirs and used for wash water, provide pre-heated water for a boiler, or used in radiant heat.

Installed Systems

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