Harnessing the Sun for On-farm Fertilizer Production

Harnessing the Sun for On-farm Fertilizer Production

Summary

Agriculture is highly dependent on fertilizer made through energy-intensive industrial nitrogen (N) fixation. As energy prices increase, so does the price of fertilizer. Biological N fixation using cyanobacteria has the potential to supply N to crops while reducing input costs and increasing energy-efficiency. Our goal is to develop and test an on-farm biological N fixation system. The primary scientific components include development and optimization of cyanobacteria-based N fixation, on-farm testing through participatory research and economic analysis. Extension fact sheets, field demonstrations, a webcast, newsletter articles and presentations will raise awareness and educate producers and professionals regarding this new technique.

Objectives/Performance Targets

Our objectives are as follows:

(1) Evaluate cyanobacterial species and growth conditions necessary for biofertilizer production;

(2) Evaluate the economic and social feasibility of on-farm or community-scale fertilizer production using a biological N-fixation system;

(3) Optimize the harvesting, processing and application of cyanobacteria-fixed N through on-farm testing;

(4) Inform the bioreactor design and utilization of biofertilizers through consultations with farmers; and

(5) Develop educational materials providing information on the production and utilization of cyanobacteria-based N fertilizer and disseminate that information to farmers and agricultural professionals through a variety of means.

Accomplishments/Milestones

Objective 1: Evaluate cyanobacterial species and growth conditions necessary for biofertilizer production

Task 1a. Evaluate the biomass production and N-fixation efficiency of test inocula under optimal growth conditions.

This task was completed in year 1, but we are continuing to expand our cyanobacterial culture collection with soil/water samples from Nebraska, Iowa, Illinois, Michigan, Pennsylvania, New York and Maine.

Task 1b. Determine the tolerance and performance of test inocula subjected to environmental stresses and variations in operational parameters from baseline conditions.

Progress was made on this task in year 1, and in the second year we evaluated additional characteristics including temperature and water quality, and we continued research on the nutrient solution needed to optimize growth.

Temperature

Two cultures (H1 and H4) were grown at four temperatures to evaluate the influence of temperature on the growth and N fixation of the cultures. The H1 culture, although it grew well previously in the laboratory, did not perform well at any of the temperatures evaluated. However, the H4 culture grew optimally in the 27-29 oC temperature range (Figure 1a), fixed the most nitrogen at 27 oC (Figure 1b) and was generally more vigorous at all temperatures than the H1 culture. Therefore, H4 was used in the pilot studies described in Task 4b.

Water Quality

We developed a laboratory method for evaluation of various growth parameters called the light box technique (Fig.2) and utilized it to evaluate the effect of water source on cyanobacterial growth and N fixation.

Three water sources were compared: distilled water, tap water and river water (a common source of irrigation water). We had used distilled water in all of our laboratory work. However, since distilled water is not practical for on-farm conditions, it was important to evaluate the impact of other water sources on cyanobacterial growth and N fixation. Although growth was highest in the distilled water, there was no significant difference in growth between the tap and river waters (Fig. 3a). On the other hand, N fixation rates were the same in the distilled and tap waters but lower in the river water (Fig. 3b).

Nutrient Solution

A nutrient solution was developed for cyanobacterial production using entirely certified organic ingredients. However, due to solubility and pH issues, this solution is lower in P and Fe than the control Allen-Arnon media (commonly used for cyanobacterial production in lab environments) and resulted in slightly lower growth rates and total N fixed (Fig. 4). Therefore, we will improve our process for making the organic nutrient solution and adjusting the pH in order to increase the P and Fe concentrations in solution. Once we have developed an organic nutrient solution in which cyanobacteria can achieve equivalent levels of growth and N-fixation as in the control Allen-Arnon media, we will begin the process of optimizing nutrient content to reduce cost and getting the new formula certified through the Organic Materials Review Institute (OMRI).

Task 1c. Determine potential methods for efficient harvesting of nitrogen from cyanobacterial cultures.

The settling behavior of different cyanobacterial strains was evaluated in order to estimate how well they would settle in a larger system (Fig. 5). Theoretical recoveries ranged from 60-90% within seven hours of settling time. The strain we selected for further technology development, H4, exhibits the highest recovery (90%).
Therefore, our harvesting methods will be based on the rapid settling behavior of the selected cyanobacterial strain. For liquid bio-fertilizer, after 24 hours of settling, the supernatant will be pumped off and recycled for continued use in the system, with minimal disturbance to the settled cyanobacteria. Then, the concentrated liquid bio-fertilizer will be drained for direct use as fertilizer. After harvest, a solar dryer will be utilized to produce solid, dry bio-fertilizer which can be stored for later use.

Task 1d. Evaluate performance of selected inocula for growth in laboratory scale bioreactors.

We compared two of our most promising cyanobacterial cultures (H1 and H4) at different temperatures and in different water sources in order to select the most-resilient culture for up-scaling under field conditions. In all cases, the H4 culture has outperformed H1; therefore, H4 was utilized in on-farm trials in the summer of 2011.

Objective 2: Evaluate the economic and social feasibility of on-farm or community-scale fertilizer production using a biological N-fixation system

We have completed evaluation of demand side factors for three main sectors of the market, including (1) certified organic farming sector, (2) conventional commercial farming sector, and (3) subsistence farming sector, with a focus on Africa.

For the certified organic sector, one major issue identified is the potential challenge of obtaining organic certification and placing BGA on the OMRI List as an approved input for organic farming. There does not appear to be a close precedent for cyanobacteria among current items on the List, and it is unclear how a BGA/cyanobacterial fertilizer would be viewed by reviewers of the application. BGA could be interpreted favorably, as a naturally occurring source, but could, depending upon the strain, be interpreted as a possible pathogenic organism that could contribute to contamination of soil or water under #167; 205.203 (c) of National Organic Program regulations (in spite of our testing that has documented the lack of cyanotoxins in the strains we have collected).

Our on-farm surveys of Colorado organic farmers largely confirm published studies of use of organic soil inputs, reporting several classes of soil amendments being used together in a portfolio strategy, including animal manures for compost, green waste for compost, finished compost, mineral soil amendments and bio-fertilizers. We also find that Colorado growers similarly prefer on-farm or local sources of soil amendments, when available, but they are highly sensitive to price. In practice, on-farm or local sourcing is mostly true for composts and materials for composting, such as green waste and animal manure. But, local sourcing is least common for bio-fertilizers, the category in which BGA fertilizer would initially fall. Because of significant heterogeneity in these different classes of amendments and unreported costs for those produced on-farm, we observe very significant variability in prices for N inputs purchased from off-farm. Conclusions that emerge are that, while organic farmers may incur significant costs overall for procurement of soil inputs, the share actually spent on bio-fertilizers is quite small, and to the extent that BGA is priced and marketed as a bio-fertilizer, demand will likely remain modest. Conversely, to the extent that it becomes more like the compost classes of inputs, produced or procured more locally at lower cost, demand will be significantly greater.

Conventional farmers included in the survey also responded favorably to the possibility of another option for sourcing nitrogen inputs, but were, predictably, highly concerned about costs and state that the BGA fertilizer would have to be priced competitively. Of course, as a strategy of diversifying and hedging against price volatility in synthetic fertilizers, some conventional farmers may be willing to pay a slightly higher per unit price for BGA fertilizer. Conventional farmers saw fertigation options, to the extent that they could cultivate the BGA in their own irrigation ponds at very low cost, as a low cost supplement to their current practices.

Analysis and farmer surveys by a team of business students from CSU visiting Ethiopia found significant interest for a biologically-based fertilizer system. Our review of the literature cautions that risk aversion and extreme price sensitivity are serious factors for adoption even of conventional fertilizers among subsistence farmers in East Africa. As such, a BGA fertilizer system for subsistence growers must be more reliable than conventional markets and very low cost.

Final steps in the economic and social feasibility evaluation will involve the supply side factors. To the extent that technical parameters of BGA productivity emerge from the rest of the project, preliminary estimates will be made of fixed and variable costs of production and related to what we have learned about demand side factors.

Objective 3: Optimize the harvesting, processing and application of cyanobacteria-fixed N through on-farm testing

Task 3a. User-informed development of cyanobacterial production and harvesting systems.

A workshop was held with our Farmer Advisory Team on January 5, 2011 in order to share our research results to date and receive their input on necessary characteristics of an on-farm bio-fertilizer production system. Farmer interest and enthusiasm for this project remains high, and their input was instrumental to the prototype design used in Tasks 4a and b.

Task 3b. On-farm testing of fertilizer produced and harvested in the laboratory.

In the winter of 2011-2012, we will use cyanobacterial bio-fertilizer in a greenhouse evaluation to determine its efficacy as compared to typically-used organic and conventional fertilizers. In spring 2012, fertilizer trials will be initiated in the field.

Objective 4: Inform the bioreactor design and utilization of biofertilizers through consultations with farmers

Task 4a. Design and evaluation of scaled-up photobioreactors and harvesting systems.

Following the farmer workshop in January 2011 (Task 3a), we designed the raceways and aeration system (Fig. 6) for installation at Happy Heart Farm in summer 2011. One hundred gallon lined ponds were constructed. The nutrient solution was continuously dripped into the pond to replace evaporation, and fish tank air pumps were used for aeration and mixing.

Task 4b. On-farm testing of scaled-up photobioreactor and harvesting system at Happy Heart Farm.

In June 2011, four 100-galllon aerated raceways were built at Happy Heart Farm for on-farm, mid-size evaluation of the technology. Two of the raceways were placed outside, and two were placed in a hoop house (Fig. 6) to evaluate the potential impact of these different climates on cyanobacterial growth and N fixation. Cyanobacteria were grown in two-week batch studies performed twice: once in June and once in July.
In both studies, the cyanobacteria in the outdoor raceways died within 24-36 hours. After evaluating alternative explanations, it was concluded that the high ultraviolet light intensity outdoors was killing the cyanobacteria. Therefore, a follow-up study was carried out to determine the best covering for the raceways that would protect the cyanobacteria from ultraviolet light, while still allowing optimum growth (Fig. 7). Buckets containing cyanobacterial cultures were placed outside and aerated with fish tank air pumps. Bucket cultures were grown with no cover (control) or covered (with one of five different materials normally used for greenhouses, hoop houses or floating row covers) and monitored over time to evaluate their performance. This methodology is useful as an intermediate step between the laboratory and field. Data is currently being analyzed from this study.

In our 100-gallon prototypes in the hoop house at Happy Heart Farm (Fig. 6), pH levels rose to above 10 and limited growth. Elevated pH can indicate a CO2 deficiency. Therefore, we are now testing an effective and affordable means of enhancing the buffering capacity of the raceways through supplying additional CO2 to the system. Bubbling CO2 into the ponds is not likely to be affordable or practical for an on-farm system. Therefore, potassium bicarbonate (KHCO3) and dolomite (CaMg(CO3)2) will be evaluated at different rates to determine the range of CO2 levels to achieve optimum growth and N fixation. Dissolved CO2 levels will be measured using alkalinity titration to document the impact of additions on dissolved CO2.

Objective 5: Develop educational materials providing information on the production and utilization of cyanobacteria-based N fertilizer and disseminate that information to farmers and agricultural professional through a variety of means.

The educational aspects of this project will be based on the on-farm research in summer 2011 and will, therefore, not begin until December 2011 (as stated in the proposal).

Impacts and Contributions/Outcomes

In the short-term, we will be developing an increased understanding and awareness of production and utilization of cyanobacterial bio-fertilizer as an alternative. In addition, we will develop the skill set necessary to produce and utilize cyanobacterial bio-fertilizer in both scientific and farming communities. In the medium-term, we will be working with organic and conventional fertilizer certifiers to achieve regulatory clearance for the use of cyanobacterial bio-fertilizer in organic and conventional farming systems. We will also develop improved decision-making abilities by both the developers and users of this technology. In the long-term, we aim for reduced fossil fuel use and greenhouse gas emissions from fertilizer manufacturing, as well as the expansion of rural jobs, a reduced-cost on-farm fertilizer source and alternative income opportunities.

Collaborators: