Jude Liu

Spring Switchgrass Harvest with a New Holland Large Square Baler

A New Holland BB9080 large square baler was used to produce large square bales of switchgrass with 900mm by 1200mm end dimensions. The switchgrass was harvested for seed in the fall and the biomass was left to overwinter on the ground. Bales of two different densities were produced and weighed in order to study the densification capabilities of the baler. Fuel consumption data and GPS data were also collected during bale production. The baler had the capability of producing switchgrass bales that approached 200 kg/m3 at 12.5% (wb) moisture content. Fuel consumption during the baling process varied from one to two liters of diesel fuel per Mg of switchgrass baled. The baler was towed at varying speeds in order to feed the baler at a constant rate. Therefore heavier windrows resulted in lower ground speeds. The most significant finding was the dramatic increase in the efficiency of bale production due to increased windrow density and decreased ground speed of the tractor and baler. There was a 31% decrease in fuel consumption in terms of L/Mg of switchgrass baled due to decreasing the ground speed from 7.45 km/h to 5.29 km/h.

Harvest Systems and Analysis for Herbaceous Biomass

Biomass is a distributed energy resource. It must be collected from production fields and accumulated at storage locations. Previous studies of herbaceous biomass as a feedstock for a bioenergy industry have found that the costs of harvesting feedstocks are a key cost component in the total logistics chain beginning with a crop on the field and ending with a stream of size-reduced material entering the biorefinery. Harvest of herbaceous biomass is seasonal and the window of harvest is limited. Biomass needs to be stored at a central location. Normally, several or many of these central storage locations in a certain range of a biorefinery are needed to ensure 24 hours a day and seven days a week supply. These centralized storage locations are commonly called satellite storage locations (SSL). The size and number of SSLs depend on the size of the biorefinery plant, availability of biomass within a given radius, window of harvest, and costs.

Evaluation of two forage harvesting systems for herbaceous biomass harvesting.

Machine field efficiency, fuel consumption, and operating costs are important aspects of biomass harvesting. Two harvesting systems were selected and examined through harvesting alfalfa (hay and silage), wheat straw, and switchgrass. One harvesting system consisted of a typical forage harvester and several forage trucks depending on the distance between the field and dump site; the other system was a self-loading/chopping forage wagon. Both systems picked up windrows prepared by a mower and a windrow merger or rake. Mowing and windrow preparation equipment were not included in the evaluation of these two systems. Moisture content (10% to 75%) and distance from field to dump site (0 to 8.5 km) were varied. These two systems were operated in adjoining fields of known area. The cycle time, weight of material picked up, and diesel fuel used by each system were recorded. The fuel use per weight of alfalfa to harvest an 8.5 km field from the silo was 2.53 and 5.59 L Mg-1 DM for the wagon and forage harvester systems, respectively, when adjusted for chop length. The wagon system required fewer operator hours to harvest a similar amount of material, but the harvester system harvested material at a faster rate of 12.3 Mg DM h-1 compared to the wagons 7.3 Mg DM h-1. The wagon yielded a much longer chop length than the harvester.

Comparison of Large Square Bale Handling Options

Large square bales currently hold great potential for harvesting and storing herbaceous biomass feedstocks. Large square bales have many advantages over both small square bale and round bale counterparts as well as other possible harvest methods. However, high cost is still a main roadblock of supplying baled biomass feedstocks. Bales production includes windrow preparation operations, baling, bale collection and storage, and on-farm bale handling. Thoroughly understanding the capacity of current technology and equipment is essential for biomass industries. Quantifying factors that affect large square bale production and handling logistics was the focus of this research. The large square bale handling capability was studied at commercial farms. Bale compression and associated operations were also studied.

Computer Model of Satellite Storage Locations for Herbaceous Biomass Handling

A commercial hay compressor was used to compress switchgrass bales and evaluate the effectiveness of the compressor operating on herbaceous biomass. The compressor operated at 0.1104 hours per ton and .5435 gallons per ton to compress the material. Assuming labor costs are 15 dollars per hour and fuel is 3 dollars per gallon, the labor and fuel costs are 1.66 dollars per ton and 1.63 dollars per ton, respectively. Including the machinery costs and 2 laborers, the total price would be 16.44 dollars per ton to compress the biomass.

Evaluation of two forage harvesting systems for herbaceous biomass harvesting

Machine field efficiency and operating costs are important aspects of biomass harvesting. Two harvesting systems were selected and examined through harvesting alfalfa, wheat straw, and switchgrass. One harvesting system consists of a typical forage harvester and several forage trucks depending on the distance between a field and the dump site; the other system was a self-loading/chopping forage wagon. Both of these systems pick up windrows prepared by a mower and windrow merger or rake. The effects of varying moisture content (10 to 75%) and distance from field to dump site were studied. The systems to be compared were operated in adjoining fields of known acreage. The cycle time, weight of material harvested, and fuel used by each system were recorded. The self-loading wagon system used significantly less fuel and required less man hours to harvest a similar amount of material. The tons of alfalfa per gallon of fuel used to harvest a field 8.5 km (5.3 miles) from the silo were .74 Mg per liter (3.08 tons per gallon) and .33 Mg per liter (1.37 tons per gallon) for the wagon and forage harvesting system respectively. Man hours required to harvest the same field were 42.56 Mg per man hour (46.91 tons per man hour) and 10.31 Mg per man hour (11.37 tons per man hour) for the wagon and forage harvesting system respectively.

Two-decade Achievements in Modeling of Soil – Tool Interactions

Study of soil-tool interaction has been carried out since 1912, but it progressed significantly after 1980’s along with the development of computer and computing technologies. Researchers have been modeling these interactions using numerical methods since then. Models developed were for evaluating the performance of tillage operations, soil movement by tillage tools, soil profile and crop residue management, and manure injection, etc. Plenty of research achievements have been received over the past two decades. Variety of mathematical models have been developed, such as numerical models using finite element analysis and computational fluid dynamics, analytical methods, empirical models, and others. To provide a clear overview of these models, this paper summarized these studies in the area of modeling of soil-tool interactions. Detailed review was focused on those models developed by the authors. Relative achievements from other researchers were also briefly discussed. Descriptions of these models included characteristics, determination of model parameters, validations, and suitable cases of applications. Limitations and potential improvements were also discussed.

Energy Consumption of Herbaceous Biomass Bulk Densification

In order to use biomass as an energy source, the challenge is that the original form of biomass material cost too much for handling and transporting. Densification is needed for cost effective handling, transportation, and storing. This study focuses on investigating the mechanical properties of energy crops during bulk densification. Switchgrass, corn stover, and Miscanthus samples were collected from fields and used in this study. The effects of chamber size, particle size/cut length, arrangement/orientation method, and harvesting time on specific energy of compressing bulk biomass crops were studied. Results indicated that larger compression chamber had significant lower specific energy consumption over the same volume reduction level. The particle length and particle orientation were also considered in this study. Results demonstrated that the parallel arrangement needed less compression energy; and the biomass with shorter particle sizes had higher energy consumption than those longer ones. Energy consumptions of the biomass harvested in different seasons were not significantly different for Switchgrass but found to be significant for corn stover.

STEADY-STATE MODELS FOR THE MOVEMENT OF SOIL AND STRAW DURING TILLAGE WITH A SINGLE SWEEP

A concept of steady-state movement, which mathematically describes the amount of soil and straw moving by a sweep, is proposed. A sweep model for the steady-state movement of soil and straw in front of a sweep was developed and validated by an experiment conducted in an indoor soil bin using three different lengths of oat straw and a 325 mm wide sweep. Existing soil-cutting models were also applied to the development of steady-state models. A three-dimensional model based on an earlier model model was developed for narrow tools; and a two-dimensional model originally proposed for earthmoving machines was developed for wide tools. The results of a validation exercise indicated that these steady-state models would predict the amount of soil and straw moving during tillage with a sweep even though the sweep was a wide tool at the tillage depth of 100 mm. However, the three-dimensional model and the two-dimensional model highly overestimated the amount of straw moving by a sweep. A possible reason was that the three-dimensional model was based on a model that was developed for a narrow blade but not a sweep. The sweep model proposed in this study provided the best results among these three models considering predicting both soil and straw moving zones. The relative error of the sweep model was 22% or less when predicting the amount of soil moving, and less than 12% when predicting the amount of straw moving. Application of existing soil-cutting models to the steady-state movement of soil and straw needs further study.

A Mathematical Model for Sub-soil Stress Estimation Using Smooth Steel Roller for Landmine Neutralization

Mechanical devices have been used to transfer force from ground surface to subsurface for the purpose of landmine neutralization. However, the data of this force transfer are not currently available. In this study, force transfer or pressure propagation in soil was theoretically analyzed using pressure bulbs. A model of sub-soil stress under the action of a steel roller was developed based on Boussinesqs equation. A smooth steel roller was tested in an indoor soil bin that is capable of testing prototype mechanical demining devices. Sub-soil forces were measured using load cells at four different depths (50, 100, 150, 200 mm). Experimental variables were roller travel speeds (1, 3, 5 km/h) and the vertical loads (20, 40, 60 kN) applied to the roller. Sub-soil forces significantly increased with increasing vertical load. For vertical loads of 40 and 60 kN, increasing travel speed reduced sub-soil forces at all four depths measured. At vertical load of 20 kN, higher travel speeds did not cause significant changes in sub-soil forces. Based on these results, methods of operating this roller to achieve a certain levels of sub-soil forces for neutralizing landmines were recommended. Experimental results were used to evaluate the model developed for subsurface soil stress distribution. The average relative error of the model was 21.8% over the test results.