Multi-Bale Handling Unit for Efficient Logistics

This paper presents a design for a feedstock logistics system to supply a bioenergy plant located in the Southeast USA, specifically Piedmont, a physiographic region covering part of five states (VA, NC, SC, GA, and AL). The design uses a perennial grass (switchgrass) as the feedstock. Harvest is done with a round baler, and round bales are stored in single-layer ambient storage in satellite storage locations. New technology, 20-bale racks, was designed as the multi-bale handling unit. The analysis shows how proper design of the interactions between the several unit operations in a “logistics chain” can be used to minimize average delivered cost for the feedstock required for 24/7 operation. Racks are loaded at the satellite storage and delivered by hauling contractors hired by the plant and controlled by a “Feedstock Manager” at the plant to insure approximately the same number of loads are received each day. Single-bale handling at the plant is eliminated, thus the truck unload time is reduced and truck productivity (tons/day) is increased. At-plant handling and storage in 20-bale racks increases plant receiving facility productivity, and gives a reduction in plant cost to supply a continuous steam of material for 24/7 operation.

Current Developments in Seeders and Transplanters for Vegetable Crops

This article is a review of the current status in planting and transplanting equipment and practices for vegetable crops. A review of horticultural and agricultural engineering literature is supplemented by information from an informal survey of members of American Society of Agricultural Engineers (ASAE) committee PM-48, Fruit and Vegetable Production Engineering, and other engineers and horticulturists working in this field. Areas covered include precision seed metering, seed placement, and high-speed transplanting with automated plant handling.

Handling of Anaerobic Digester Supernatant Combined with Full Nitrogen Removal

In order to meet future standards of 8 mg/l total-nitrogen, 0.3 mg/l total-phosphorous and 10 mg/l BOD7, the Klagshamn wastewater treatment plant in Malmö has to be upgraded. A concept where the standards could be met within the existing activated sludge plant has been found. Primary precipitation is followed by a single sludge post-denitrifying process where methanol is added as external carbon source. The system is high rate with only 7 hours retention time in the biological reactor. In order to improve the process stability and make a future increase in load possible within the existing plant, handling of digester supernatant has been examined. The normal operation of the sludge handling system leads to discharge of a supernatant with a high content of ammonium. The load from the supernatant made about 15% of the total-nitrogen load on the plant on an average basis but could reach up to 65% during working hours. This extra load could be recognized as peaks of ammonium and nitrate in the effluent. The digester supernatant and its impact on daily variations in ammonium and nitrate have been examined in detail and the examination has formed the basis for a mathematical modelling of the system in order to test strategies for optimized handling. Equalization of the supernatant flow, separate nitrification of the supernatant, and completely separate treatment of the supernatant have shown to be able to improve process stability. Flow equalization seems to be as effective as the two other more expensive and complicated solutions.