14-0619 v2.X Bio-digesters


Our project is a Tribal College facility with nine acres of agriculture. The facility will include a commercial kitchen, a residence to support agriculture labor, a teaching kitchen with five residential-type stoves, and two laboratory classrooms each equipped with Bunsen Burners. The agriculture will require the use of a diesel tractor due to its scale. The project team realizes that there is an exception for gas use in both a commercial kitchen and for Bunsen burners. The project team also realizes that bio-gas and biomass combustion solutions are frowned upon. 

We are seeking confirmation on our approach. Originally we were going to pipe in gas for the aforementioned uses. However, it was recently requested by the client for the team into biodigesters to supply methane for the gas equipment and bio-diesel for the tractor. Our proposed approach is to install two biodigesters on site, one to produce about 500 CCF of methane to supply the gas for the ranges and Bunsen burners and one to produce about 500 gallons of bio-diesel for the tractor. The intent is to grow the agri-products on-site that will become the fuel for the methane digester and to capture waste grease and oil from the Tribal casino’s kitchen, currently located on mile from the project site, for the bio-diesel digester. Excess bio-diesel will be used by tribal lawn equipment or fleet vehicles; extending the impact of the biodigester beyond this project.

We are also seeking exception for the gas residential- style stoves for use in the on-site residence and in the teaching kitchen. We started to explore induction ranges but opted not for these because they are meant to emulate home-kitchens and sadly induction ranges are inaccessible for most of the student population. We then thought about electric stoves but they are grossly inefficient. Additionally, we realized we’d be capturing methane on site of the commercial kitchen anyway so we thought it would be more appropriate to use this for the teaching kitchen as well.

No combustion will be used to supply any other building needs and we are currently targeting to supply about 30% more energy than our preliminary EUI suggests we need with a 50% - 50% split between wind and PV energy production. Extra power will be converted to thermal energy and stored in our geothermal well field system. When the well field is at capacity and the on-site battery backup system, which is sized to provide the entire facility emergency power for two days, is full, electricity will be distributed to adjacent tribal building or sold back to the grid.

Our guiding principles demand restorative solutions and we feel this energy approach fulfills that self-imposed project imperative.


Yes, your approach for a bio-digester is an acceptable strategy. The tractor is outside of the scope of the Living Building Challenge.An exception for using a gas stove in the on-site residence will not be granted, several residences have used induction stoves with great success.The existing exception for the commercial kitchen may apply to the teaching kitchen but more information is needed around the function of the kitchen to determine that.

Post ID 2019

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