Division of Agriculture and Natural Resources
Division of Agriculture and Natural Resources
Division of Agriculture and Natural Resources
University of California
Division of Agriculture and Natural Resources

Posts Tagged: sustainable agriculture

Biodigesters turn food into electricity, but can they also create fertilizer?

On a recent late-summer Wednesday, a freight container filled with cases of expired Muscle Milk protein drink awaited unloading at the UC Davis Renewable Energy Anaerobic Digester (READ) while a front-loader scooped heaps of spoiled vegetables into a mechanical processor. Nourished by a diet of assorted food waste from the UC Davis campus and area restaurants and markets, READ harnesses the activity of billions of microbes to produce biogas capable of generating 5.6 million kWh per year of clean electricity for UC Davis.

Out of date products are sent to the aenorobic biodigester to be converted to energy and now fertilizer

But a by-product of READ and other anaerobic digesters – the slurry of leftover solid and liquid material, or digestate – has caught the attention of UC Davis researchers interested in “closing the loop” on food production, consumption, and waste. When processed through an anaerobic digester, organic materials like food discards, expired or off-spec food products, or animal manure can be transformed into concentrated biofertilizers and soil amendments that are highly effective and easily applied to crops.

In an interdisciplinary collaboration at the Russell Ranch Sustainable Agriculture Facility, funded by the California State Water Resources Control Board and the California Department of Food and Agriculture, UC Davis faculty and students have developed a pilot-scale process for commercial production of several forms of this biofertilizer using digestate from READ and other nearby digesters. They are also evaluating their effects on yield and other agronomic metrics in corn and tomato field trials – paving the way for farmers and growers to take advantage of a highly sustainable source of plant nutrition.

The challenge and opportunity of fertilizer from anaerobic biodigesters

The digestate from READ and other digester facilities can be applied directly to soil as a fertilizer, but, because it has a limited shelf-life, it usually must be applied to land in the immediate region of the facility. With the input of food waste that can vary widely from day to day, a facility's digestate is inconsistent in texture and composition, making it difficult to transport and apply to fields using common farm fertilizer equipment.

Filtering and drying this digestate, however, results in solid and liquid forms that can be concentrated, homogenized, easily transported, and applied to soil through existing drip irrigation systems or surface spreading equipment.

This process could allow farmers and growers located further away, and working with common irrigation and fertilizer application equipment, to supplement or replace their synthetic fertilizer consumption with biofertilizers from food waste or animal manure.

How do biodigestate products measure up to synthetic fertilizers?

The research, co-led by professor Ruihong Zhang from the UC Davis Department of Biological and Agricultural Engineering (who also designed READ in partnership with Sacramento-based tech company CleanWorld) and Professor Kate Scow from the Department of Land, Air, and Water Resources, developed pilot-scale systems to efficiently and consistently separate the solid and liquid portions of food- and manure-based digestates. The researchers then examined the nutrient composition of the solid and liquid biofertilizer products, finding that biodigestate-based fertilizers contain valuable nutrients and microbes not found in many synthetic fertilizers.

In current field trials, the researchers are investigating the effects of each of the biofertilizer products on crop yield and quality. Their preliminary results show that it is possible to grow irrigated processing tomatoes and short-season corn using biofertilizer products as the sole source of fertilizer. The origin of the fertilizer matters, however – manure-based liquid fertilizer formed additional large particles after the final filtration, creating concerns about clogging the drip irrigation system. The team thinks an environmentally benign chemical sometimes added to manure digesters to clean the biogas may be the culprit of the problem, but future research is needed. The solid biofertilizer pellets they developed show much promise, as they can be applied using existing methods for spreading compost and can be economically transported farther away from the digester.

In addition to better understanding the best processes for producing and using the biofertilizers, further research is needed to understand how much of the nitrogen in each of the fertilizer products is available for uptake by the crop, as well as economic analyses to determine the commercial-scale production and transportation costs. The researchers will be able to narrow in on the agronomic and economic potential of biofertilizers through the upcoming analysis of the yield of the corn and tomato experiment plots at Russell Ranch. The results of a tomato experiment recently showed that the digestate fertilizers produced just as much fruit as a popular synthetic fertilizer.

UC Cooperative Extension advisor Gene Miyao looks at biofertilizer in its various stages, from raw waste to fertilizer

Interdisciplinary research for agricultural innovations

Russell Ranch, a program of the Agricultural Sustainability Institute, is designed as a shared space for interdisciplinary research and innovation. The biofertilizer research, among other active projects at Russell Ranch, is an example of the fulfillment of that intention. “The soil scientists are learning engineering, the engineers are learning biology, and the biologists are learning about soil,” Professor Zhang remarked.

The exchange also extends beyond the university: a recent UC Davis Biofertilizer Field Day drew attendees from the UC Division of Agriculture and Natural Resources, several public agencies, the agricultural sector, other universities, nonprofits, entrepreneurs, and food processors. If the research continues to illuminate a way forward for biofertilizers, these audiences may fill important roles in bringing this new technology into practice – and in recycling your lunch leftovers back into a more efficient and sustainable food system.

More information: UC Davis READ, Russell Ranch, and the biofertilizer research

The UC Davis Renewable Energy Anaerobic Digester was unveiled in 2014 as the nation's largest anaerobic biodigester on a college campus, and represented a unique private-public partnership. Professor Ruihong Zhang invented the anaerobic digestion technology used by CleanWorld, which developed it into one of the most advanced commercially-available digester systems in the country.

Russell Ranch Sustainable Agriculture Facility is a “living laboratory” for interdisciplinary field research and innovation. Its flagship project, the Century Experiment, measures the long-term impacts of energy, water, carbon, and nitrogen inputs on agricultural sustainability in the flagship Century Experiment.

The biofertilizer research collaboration includes Zhang Lab graduate students Tyler Barzee and Hossein Edalati, Scow Lab postdoctoral researcher Daoyuan Wang, and Russell Ranch manager Israel Herrera. Collaborating institutions include CleanWorld, California Bioenergy, New Hope Dairy (Galt, CA), Fiscalini Dairy (Modesto, CA), and Sacramento Municipal Utility District.

Posted on Thursday, September 15, 2016 at 8:30 AM

Agroecology, internationally and at home

For many years, a key international strategy to ending hunger has been to grow more food: push for higher yields, develop ways for farmers to intensify their farming, focus on technologies that drive both. But that focus may be shifting towards another strategy that better accounts for the environment and human well-being – agroecology.

Barbara Gemill-Herren, a retired officer from the Food and Agriculture Organization of the United Nations, spoke recently at UC Davis of the ongoing process at the United Nations to determine an international strategy for agricultural development.

For many, a new paradigm needs to strike a balance between supporting small-scale farmers, supporting healthy ecosystems, and bringing in the technology that can help meet changing challenges for growers.

Agroecology has recently entered the vocabulary at the UN as a potential unifying principle for agricultural development.

As its name suggests, agroecology studies the ecology of the entire food system, focusing on environmental, economic and social dimensions and how they interact with one another.

Beyond that definition, the term is used and understood differently by different groups. For some, agroecology is a scientific discipline, for some it represents a way for farms to be managed. For others, it is a social movement that brings local and indigenous knowledge to the center of agricultural development.

At the United Nations meetings on agroecology, each of these interpretations of agroecology have been on the table for discussion — how they can be used to improve international agricultural development will be revealed in global conversations in the years to come.

Agroecology endowment at UC Davis secures research opportunities

Here at home, agroecology is on the upswing as well. Funding for a $1 million endowment in agroecology was recently secured at UC Davis to help fund the research, education, and outreach conducted by an agroecology faculty member. Collaborating with UC Cooperative Extension farm advisors from UC Agriculture and Natural Resources will be a key way for future work to connect with growers. 

Endowments offer reliable funding every year that allow faculty to plan longer term research. For research like agroecology that looks at how agricultural systems function, that flexibility is important, if not essential.

Tom Tomich, director of the Agricultural Sustainability Institute, which helped raise funds for the endowment, says, “The endowment represents at a broad spectrum of philanthropists and shows that scientific approaches to agroecological systems science is appreciated by our stakeholders in California. It's a form of legitimization of systems science applied to agriculture.”

Opportunities for collaboration between researchers and farmers

Amélie Gaudin, assistant professor of agroecology at UC Davis.
For Amélie Gaudin, assistant professor of Agroecology at UC Davis, agroecology is on a promising path toward sustainability for California agriculture. Gaudin started working at UC Davis in 2015 and is building her research and community relationships.

Below are some thoughts from Gaudin on how she approaches her work and how she sees this agroecology endowment impacting research and education at UC Davis.

How do you define agroecology?

There are different definitions of agroecology for different people. Mostly I see it as research to understand dynamics of ecological processes and to apply ecology to agricultural systems design. Agroecology merges the food security and production goals of agriculture with resource use efficiency goals and environmental goals in agriculture. For many people, agroecology is a social movement to make systems socially just. While my focus is largely on biological processes, it's also about learning from small-scale farmers who have been successful in their management practices to see how we can translate those successes to other contexts. And that is very social in nature.

At what scale do you research?

Usually we tend to work at the field scale, looking at cropping systems and the landscapes that surround them. Looking at the field, we can see how the long term management of a farm has affected the soil and its functioning as well as productivity and provision of multiple other ecosystem services. Looking at the surrounding landscape, we can understand what the natural environment has provided to the farm system, and what the farm system provides back to the natural environment. Sometimes we look a meter out, sometimes a kilometer out.

But beyond just the space we look at, we're really looking at time. Nature takes time. When you look at the field, it's an observation of what has been going on there for a very long time.

How does agroecology research work with farmers?

Working with farmers helps give research the long-term lens and management gradients we need to understand these agricultural systems, and gives us a landscape lens that many research fields can't provide. It also helps relate our research to production constraints that farmers have.

There is also tremendous innovation in what farmers are coming up with. They have a specific problem and they usually have tried specific solutions. They test things out, they monitor their fields and see results, but maybe don't understand fully the underlying mechanism and potential impact on the environment. We try to get to the why; we try to connect the dots to enable scaling up and better understanding of the ecological processes regulating resource use efficiency.

We're also looking a lot at resilience to stresses. And we find more and more interest in this because resources are not plentiful anymore and we now have to produce more with less. So how do we build resilience to the multiple stresses that come along? Are there ways that the management of a farm can impact productivity when a stress like drought occurs?

We have a lot to learn from small growers and a lot to learn from growers who have constrained resources about what they have been implementing and experimenting with. How can we transfer those practices to different environments? How can we scale them up?

How can we make it work in large-scale agriculture? There's a huge opportunity there. I want to see agroecological approaches to management implemented all over the Midwest, all over the Central Valley. I think agroecology is compatible with large-scale agriculture and critically needed.

How do you approach research questions?

I start with the problems a farmer didn't have. One project started with a tomato farmer who didn't have the same insect problem that surrounding farms had. So we ask, what is he doing that created this insect resistance, and how can that be used by other farmers? We met with several different farmers to discuss the issue, and wrote a grant to investigate specific hypothesis across a management gradient.

We're now working with five different growers and using Russell Ranch, our long-term agricultural research facility, as a benchmark.

I think conversation with farmers and their advisors is critical to develop relevant research questions and alternatives which have conservation of natural resources, biodiversity and provision of ecosystem services as a basis for improvement. It is also important to keep a positive feedback loop and bring results back to the community to foster farmer-to-farmer knowledge transfer.

What excites you about this new investment in agroecology?

The context of agriculture is changing and we now have a tremendous opportunity to promote agroecology as a viable and necessary strategy to build the sustainability and resilience of our agriculture. Farmers are seeking solutions, they are aware and interested. With climate change and depleted resources becoming more of a reality, growers are interested in putting soil improvement and ecological principles back into their management framework. And I think we ultimately care about the same things, we just need to find common ground and start speaking the same language. To do it we have to be open minded, both on the researcher and farmer side.

Investment in agroecology will help us reach this objective and gives us an opportunity to think outside of the box. This gives an opportunity to be creative, cope with some of the pitfalls of science funding and take a participatory approach to interdisciplinary research to design holistic solutions that better use nature for a sustainable agriculture.

Posted on Wednesday, April 6, 2016 at 8:35 AM
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