Grantee Research Project Results

Final Report: Feasibility of on-farm microalgal cultivation for dairy feed supplement through integration of anaerobic digestion of farmwaste

EPA Grant Number: SU840583
Title: Feasibility of on-farm microalgal cultivation for dairy feed supplement through integration of anaerobic digestion of farmwaste
Investigators: Rogers, Shane , Ferro, Andrea , Grimberg, Stefan J.
Institution: Clarkson University
EPA Project Officer: Brooks, Donald
Phase: I
Project Period: August 1, 2023 through July 31, 2024
Project Amount: $25,000
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Research Category: P3 Awards

Objective:

Methane (CH₄) is a greenhouse gas 25 times more potent than carbon dioxide, and an estimated 27% can be traced to agricultural sources. One of the largest sources of methane in the agricultural setting comes from dairy and beef cattle. Recent research to substantially reduce methane release from cows has found success with supplementary microalgae diets. While promising, the feasibility of growing and incorporating algae into livestock diets on a large scale has technological, economic and societal challenges. We are proposing a closed-loop system for growing algae on dairy farms to address this problem. Using an anaerobic digester, manure from the cows on site will be used to generate energy, which will then be used for lighting and heating in the algae photobioreactors. The algae will be used to supplement the livestock feed, reducing the methane emissions. Our main objective is to study the feasibility of growing microalgae using energy and nutrients produced via anaerobic digestion of farm waste. To do so, we investigated the cultivation of Chlorella vulgaris microalgae grown under anaerobic and aerobic conditions using digester effluent as a nutrient source for the algae. Laboratory studies complementing the on farm experiments consisted of evaluating best practices to recycle water for algae cultivation.  A process model of the integrated algae/digester system was developed using mass and energy balances to determine the optimal process parameters.

Summary/Accomplishments (Outputs/Outcomes):

Reducing the emission of greenhouse gases from dairy farms will have a direct positive impact on the planet. By localizing feed production and on-site energy, the need for additional transport and excess resources is eliminated, resulting in a more sustainable approach to agriculture. Additionally, the cost of feed and import will be reduced and the health of livestock will improve, resulting in more prosperous sales. The potential implementation of this project directly benefits a wide range of stakeholders. Workshops were held for farmers to gauge and increase understanding for system adoption. Outreach and educational opportunities was provided to the  K-12 school districts within the local community.

Conclusions:

Results from this Phase I project determined that growing microalgae from the energy and nutrients produced via anaerobic digestion of farm waste allowed for sufficient algae at the farm providing feed supplement for cows. We evaluated a 3000 cow dairy operation we determined that the digester will sufficient energy and nutrients to allow for the cultivation of algae that is needed as feed additive for the dairy cows reducing their enteric methane emissions. Overall, the closed loop system would reduce green house gas emissions by 80% for a conventional dairy farm, generate net annually energy of 6.7 GWh at an estimated payback period of approximately 6 years.

Supplemental Keywords:

agriculture, anaerobic digestion, climate adaptation, greenhouse gas reduction, life cycle assessment