Conceptual design of high-density plant cultivation system with on -line extraction.

Abstract

Industry needs to examine alternative approaches to its traditional chemical manufacturing processes to promote pollution prevention and cleaner production. We have been investigating the feasibility of producing valuable plant-derived chemicals through high-density plant cultivation on mobile platforms in an automated greenhouse and through optimizing light delivery and thus enhancing the photosynthetic efficiency via engineering means. Based on a simple mathematical model to describe light attenuation in a high-density plant cultivation system, we propose that a more efficient way of delivering light can be achieved by supplying light from both the top and through the bottom of the plant. Based on this model, we designed a mobile platform for plant cultivation in which light illuminates from both the top and the bottom and found that for the same total light energy, the specific growth rate was 30% higher for these illuminated plants than for plants grown with a conventional lighting source from the top. Furthermore, a three-dimensional (3-D) plant cultivation system using multiple layers of these cultivation platforms is proposed. Analyses show a further increase in the efficiency of light utilization by the plants based on their optimal photoperiodic schedule. Using peppermint plants as the model plants, we have found that the 3-D cultivation system can nearly triple the plant productivity over the conventional 2-D cultivation method using the same area under a constant light source or with a natural solar radiation cycle. We have also investigated the feasibility of using on-line ultrasonic extraction to release desired plant metabolites intermittently while leaving the plants in a viable and productive state. The ultrasonic effects of plant metabolite release were found to be both of a thermal and a non-thermal nature because a stable source of ultrasound was not used in our experiments. The amount of the product released and the degree of damage varies directly with the duration of transient nature of ultrasonic treatment. But, we have demonstrated that the plants can be extracted repeatedly without losing their viability even though the optimal treatment for plant metabolite release has not been achieved.