Progress 05/01/23 to 04/30/24
Outputs
Target Audience:Academic (university) researchers Undergraduate and graduate students studying Entomology and Agricultural Engineering University personnel engaged in catering, dining services, and waste management Changes/Problems:The steady-state condition was reached a few months later than anticipated because we deliberately chose to demonstrate the importance of monitoring abiotic conditions by first setting up a "minimal monitoring" approach, followed by a second phase where we consistently monitored temperature, humidity and pH of the biodegrading waste and ambient temperature and adjusted our maintenance tasks accordingly. This was critical as it shows the importance of monitoring those factors, and in turn the importance of automating the monitoring operations, as they are labor intensive. A few challenges were already noted from the robotic arm prototype, justifying some of the proposed modifications described in the previous section. A broken pH sensor resulted from the physical contact of the latter with the substrate. While the sensor was equipped with a spear to improve its robustness, the probe, which had a glass bulb, broke, delaying experimentation. Additionally, given the initial complexity in operating the arm, the debugging process between researchers of different fields was also time consuming, something which can benefit from the addition of internet connectivity and therefore instant debugging to the greenhouse. We have also faced some challenges in recruiting personnel for the project on the engineering side. What opportunities for training and professional development has the project provided?A PhD student, William Samson, has been trained to farm BSF to produce frass thanks to this project. He is now writing up this work for publication and will include these activities in one of the chapters of his dissertation. Three undergraduate students (Hewitt Plunkett, Ricky Le and Jaden Kim) are also working on this project and will be co-authors on forthcoming work. During this work, the graduate and undergraduate students learned important skills in task management, troubleshooting and data recording. William gained experience in presenting his research through poster presentations at several local venues. William Samson was mentored by the former (Marco Gebiola) and current (Kerry Mauck) PI, and in turn he mentored the three undergraduate students, thus gaining experience in mentoring students through a research project. A post-doctoral researcher (Caio Mucchiani) was mentored by the co-PI as he worked on the robotic arm with sensor array. How have the results been disseminated to communities of interest?The work completed in year 1 has been presented by former PI Marco Gebiola, now Associate Professor at the Department of Agricultural Sciences of the University of Naples Federico II, Italy at a monthly outreach event by an invited talk (in Italian) on March 20, 2024. The work was also discussed at an outreach event for STEM middle schoolers at the UCR Campus (May 2024) and an on-site tour and presentation to compost industry representatives was made in April 2024. What do you plan to do during the next reporting period to accomplish the goals? Add robotic arm that will allow to partly automate the maintenance operations, that is, waste loading, unloading and mixing. Compare side-by-side the fully manual and semiautomated system to evaluate yields of frass and quantify costs and cost savings of the semiautomated system Demonstrate the application of the semiautomated system using a homogeneous agricultural waste (citrus?) instead of catering waste Substitution of the pHsensor for less recalibration needs and more robust measurements, also considering the modified housing for the same Addition of a thermal camera for larvae cluster identification at the BR1 bins, as proposed in1. Addition of network connectivity for remote monitoring of the sensors and greenhouse. Consideration of the above for an informed sampling of the robot arm, guided to detect conditions at clusters, while also sampling them. Implementation of a remote watering system. Design and implementation of a mixing mechanism for the BR1 bin. Consider all previous elements for a full automated solution to the sampling, watering and mixing problems as required by the method. Footnotes: 1. https://ieeexplore.ieee.org/document/9926430
Impacts
What was accomplished under these goals?
?Project impact Unusable crops are considered waste to be removed at the farmer's expense. Reintroduction of insect decomposers into agricultural systems can alleviate waste removal costs, rapidly generate usable products (fertilizer), and lead to new revenue streams (insect biomass). The Black Soldier Fly (BSF) is an effective decomposer of any type of organic matter, and is used worldwide for waste management, production of fertilizer (frass), and as feed for livestock, aquaculture, and pets. However, BSF rearing by the standard "batch" method (carefully measured cohorts of larvae with set quantities of waste) currently requires substantial human labor, which hinders on- farm use. An alternative "steady state" rearing system involves continuous rearing of BSF in bioreactors and is less labor intensive, but still requires some human maintenance. These maintenance tasks are targets for introducing cost-conscious sensing and automation. The goal of this seed-grant project is to engineer, build, and test a prototype automated steady state system suitable for on-farm use. We will accomplish this goal through a productive and established collaboration among two entomologists, the inventor of the steady-state system, and an electrical/computer engineer. This project directly aligns with the goals of the Biorefining and Biomanufacturing priority within the Agricultural Systems and Technology program area. By automating on-farm BSF rearing, we will "expand utilization of waste in agricultural systems" and "engineer new products that utilize materials from agriculture." Our project also addresses the AFRI long-term goals to ensure "efficient use of on-farm resources" and increase "integration of natural biological cycles and controls" in agricultural systems. 1) Major activities. Obj. 1. The first phase of the project was to set up a BSF farming system that would reach a steady-state production of insects and their frass. The modular system was assembled in mid-July 2023 by the entire team (PIs and co-PIs, consultant, graduate and undergraduate student) in one day. Once the procurement of catering waste was ensured through campus dining operations, in August 2023 a BSF rearing was initiated by inoculating 2 consecutive batches of about 12 kg of waste each with 10,000 BSF neonate larvae on Aug 18 and 22. About 12-15 kg of catering waste would be added every 4 days on average and mixed with the existing waste, water and bulking agents (wood chips). At the completion of the first generation, the emerged adults would lay eggs inside buckets where incoming fresh waste was stored for about a week prior to being introduced in the system, so that upon mixing fresh and old waste eggs and younger larvae would be added to the waste mixture. This guarantees a steady supply of larvae of any age, which would then continuously develop into prepupae that would self-harvest by climbing the walls of the BR1 container (large bin of about 1.5 m2), fall first into the gutters surrounding the BR1 containers and then inside a collection bucket. Prepupae thus collected would be weighed every loading cycle (4 days) and stored in plastic boxes to allow for pupation and subsequent adult emergence. When after several cycles of loading the waste inside the BR1 reached a depth of about 10 cm, three smaller bins (hereafter BR2s, about 0.24 m2 each) stacked on top of each other on a rack placed onto the BR1 would gradually be filled with overflowing waste, and upon the following loading cycled mixed back with BR1 old and fresh waste and larvae and then redivided among the 3 BR2s. When these BR2 were filled, 2 more BR2s, also laid on top of the BR1 but on a separate stack, would be filled. These BR2s (hereafter spent waste BR2s) would not be mixed any longer with incoming fresh waste but would be left to dry for over about a month and stored separately as airdried spent waste (frass). Initially, we followed a "minimal monitoring" low labor approach where the only metric used to assess the achievement of steady state was the yield of prepupae, calculated as kg of prepupae harvested per square meter per day (steady state = 0.50 kg prepupae/m2/d). After 6 months we switched to a monitored approach where we would manually monitor ambient and waste temperature, waste humidity and waste pH. After about 3 months of manual monitoring, we began testing a robotic arm and sensor array that would monitor those same conditions, as well as greenhouse (CO2, CH4) and nuisance (NH3) gases. A custom-made end-effector able to house all mentioned sensors was adapted to the robot arm (an Interbotix Rx150 model). Consistency in sampling location and uniformity in data collection led to the choice of a low-cost solution for the selected arm. We determined that only three degrees of freedom were required which improved the arm payload capability necessary to withstand the weight of the custom-made end effector and sensor array. For the end effector, we used renewable and biodegradable resources such as PLA (polylactic acid) plastic. The collection of sensors affixed to the end effector communicated with an Arduino Mega Microcontroller. The microcontroller, in turn, transmits real time data via serial communication to a minicomputer using ROS2 protocol. The minicomputer is able to receive direct commands from the researcher, controlling the motion of the robot arm and locally storing all the data. Connections of sensors to the arm were insulated against greenhouse conditions. 2) Data collected During the "minimal monitoring" phase every loading cycle we recorded the following data: weight of fresh waste added, volume of water added, weight of self-harvested prepupae. Approximately every 2 months we would also record the weight of airdried frass obtained. During the "multi-metric monitoring phase", we also recorded: ambient and waste temperature, waste humidity at 2 different depths, waste pH. During the "semi-automated monitoring phase", in addition to these abiotic conditions, we also recorded: CO2, CH4 and NH3 before and after loading the waste 3) Results The "minimal monitoring" phase did not lead to steady-state farming. The goal of 0.5 kg/m2/d of prepupae was reached 3 times but could not be sustained for more than six weeks and anaerobic conditions associated with strong odors arose on two occasions, as it was difficult to adjust the amount of water and bulking agents to be added. The "multi-metric monitoring" phase led to steady-state conditions in a matter of few weeks, with an average yield of 0.50 kg/m2/d of prepupae sustained for over 4 months. All monitored parameters provided useful insights that quickly optimized temperature, pH, and moisture levels. The "semi-automated monitoring" phase reduced the amount of time spent by student workers monitoring the abiotic conditions to a matter of few minutes. The inclusion of the robot arm addresses the need for physical interaction with the substrate for sampling (for sensors such as pH and moisture), while also allowing for the measurement of greenhouse and nuisance gases near the substrate surface. 4) Key outcomes We have confirmed the importance of monitoring abiotic conditions to reach steady-state level for BSF farming. In particular, the following key indicators have emerged: - if larvae are feeding and developing optimally, the waste should be about 5°C warmer than ambient temperature - pH of the waste should oscillate minimally around a value of 8 - in Southern California weather conditions, humidity of the waste can be as low as 30% and usually around 60% when larvae are at their best biodegrading performance. We have also engineered a cost-conscious robotic arm that drastically reduces the labor input necessary to monitor abiotic conditions, and that at the same time allows to monitor also other environmental parameters (gas emissions). Objectives 2 and 3 will be tackled in year 2 of the project
Publications
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