Economic evaluation of manual and robotic transplanting of plant cuttings

摘要

Transplanting of unrooted plant cuttings into propagation trays is a manufacturing process that requires considerable labor, especially during the peak season. The objective was to benchmark the labor efficiency of the manual transplant process and evaluate return on investment of automation. Data were collected on the transplanting process of 14 large U.S greenhouse companies. Manually transplanting required 6.4±2.7 s (mean±st.err.) at a cost of $0.023±$0.003 per cutting. Differences in labor cost resulted from both the plant type produced in each location and the hourly wage which ranged from $9.23 to $18.66 and averaged $12.49±0.78. To evaluate automation, data on labor, cuttings transplanted, and costs of automation were collected from fivegrowers using transplant robots. A return on investment spreadsheet model was developed that allowed customized analysis of individual greenhouse businesses. The number of cuttings transplanted in the sampled firms under investigation averaged 29.3M cuttings per year, with a weekly peak of 2.1M cuttings. Four transplant robots capable of transplanting 2000 cuttings per hour operated for up to 76 h per week during the peak and transplanted 17.4M cuttings per year (59% of the total). This equipment had acapital cost of $500,000. The average automated cost was $0,010 per cutting compared with $0,014 for manual transplanting. With these assumptions, the robotic transplanter would yield a yearly saving of $62,488, and would reduce labor requirement duringthe peak week by 9 full-time equivalents (15% of total workforce). However, with a 5% discount rate the net present value (NPV) over 10 years was slightly negative (-$17,487). In contrast, if wages increased to $20 the NPV was highly positive ($960,358).Results emphasize the need for careful and customized analysis by growers to ensure profitability from automation. Results will help growers highlight management practices to improve efficiency of the manual process, and evaluate how robotics could benefit producers in terms of labor cost and availability.