Analysis of Storage Methods and Tarping Practices for Corn Stover Bales

In 2011 and 2012, Iowa State University conducted storage trials for large, rectangular corn stover bales to determine the most effective storage method for companies and farmers harvesting corn stover. Over 2000 bales were used for different storage trials, and five storage configurations were tested. Standard outdoor tarped and indoor stacks proved to be the most effective in preserving bale quality and limiting deterioration, with dry matter losses below 5% in 2012. Moisture content of the bales was studied by collecting pre and post-storage moisture contents of the bales. It was found that all bales, no matter the initial moisture content, would dry down to an industrial-acceptable moisture content of nearly 15%, if stored appropriately. Bale temperatures, which are an indicator of moisture content and microbial activity, were also studied to support the dry matter loss and moisture content data, as well as to ensure these stacks were not creating opportunities for bales to self-combust. In both years of temperature studies, no bales were found to reach temperatures near self-combustion level

Investigation of Process Variables in the Densification of Corn Stover Briquettes

The bulk density of raw corn stover is a major limitation to its large-scale viability as a biomass feedstock. Raw corn stover has a bulk density of 50 kg/m3, which creates significant transportation costs and limits the optimization of transport logistics. Producing a densified corn stover product during harvest would reduce harvest and transportation costs, resulting in viable pathways for the use of corn stover as a biomass feedstock. This research investigated the effect of different process variables (compression pressure, moisture content, particle size, and material composition) on a densification method that produces briquettes from raw corn stover. A customized bench-scale densification system was designed to evaluate different corn stover inputs. Quality briquette production was possible using non-reduced particle sizes and low compression pressures achievable in a continuous in-field production system. At optimized bench settings, corn stover was densified to a dry bulk density of 190 kg/m3. Corn stover with a moisture content above 25%wb was not suitable for this method of bulk densification, and greater cob content had a positive effect on product quality

Production Scale Single-pass Corn Stover Large Square Baling Systems

A single-pass combine baler was operated in Central Iowa for the harvest of 2012 in a production scale setting. The combine’s performance was monitored with a telemetry data logger. The combine was able to harvest 2227 bushels (62.4 tons) of grain per hour on average and 18.8 tons of stover per hour on average. A complete quality analysis system was evaluated for the single-pass combine through the harvest of 2012. On board baler scales were tested showing a less than 1% difference in average weight between calibrated platform scales and the baler scales. Also, a microwave moisture meter was evaluated on a separate baler which showed between the 10% and 29% moisture level an R2 value of 87%

Effect of Torrefaction Process Parameters on Biomass Feedstock Upgrading

Biomass is a primary source of renewable carbon that can be utilized as a feedstock for biofuels or biochemicals production in order to achieve energy independence of energy importing countries. The low bulk density, high moisture content, degradation during the storage, and low energy density of raw lignocellulosic biomass are all significant challenges in supplying agricultural residues as a cellulosic feedstock. Torrefaction is a thermochemical process conducted in the temperature range between 200°C, and 300°C under an inert atmosphere which is currently being considered as a biomass pretreatment. Competitiveness and quality of biofuels and biochemicals may be significantly increased by incorporating torrefaction early in the production chain while further optimization of the process might enable its autothermal operation. In this study, torrefaction process parameters were investigated in order to improve biomass energy density, and reduce its moisture content. The biomass of choice (corn stover) at three levels of moisture content (30%, 45%, 50%) was torrefied at three different temperatures (200°C, 250°C, 300°C), and reaction times (10min, 20min, 30min). Solid, gaseous, and liquid products were analyzed and the mass/energy balance of the reaction was quantified. Overall increase in energy density, and decrease in mass and energy yield was observed as process temperature increased. Initial biomass moisture content affected energy density, mass, and energy yield especially at low process temperature, and high moisture feedstock

Water vapor adsorption on torrefied corn stover

The equilibrium moisture content (EMC) of biomass affects transportation, storage, downstream feedstock processing, and the overall economy of biorenewables production. Torrefaction is a thermochemical process conducted in the temperature regime between 200 and 300°C under an inert atmosphere that, among other benefits, aims to reduce the innate hydrophilicity and susceptibility to microbial degradation of biomass. The EMC of raw corn stover, along with corn stover thermally pretreated at three temperatures, was measured using the static gravimetric method at equilibrium relative humidity (ERH) and temperatures ranging from 10 to 98% and from 10 to 40°C, respectively. Microbial degradation of the samples was tested at 97% ERH and 30°C. Fiber analyses were conducted on all samples. In general, torrefied biomass showed an EMC lower than raw biomass, which implied an increase in hydrophobicity. Corn stover torrefied at 250 and 300°C had negligible dry matter mass loss due to microbial degradation. Fiber analysis showed a significant decrease in hemicellulose content with the increase in pretreatment temperature, which might be the reason for the hydrophobic nature of torrefied biomass. The outcomes of this work can be used for torrefaction process optimization, and decision-making regarding raw and torrefied biomass storage and downstream processing

Understanding management practices for biomass harvest equipment for commercial scale operation

As second generation biofuels approach commercial scale production, a large fleet of harvesting equipment is required to meet feedstock demand. In the Midwest United States, agricultural residue, such as corn stover, has been identified as a readily available feedstock. Multi-pass corn stover harvest requires the in-field operations of shredding, baling, and stacking. Proper management practices are required to keep machines running at maximum efficiency in order to reduce cost and harvest enough material to meet processing demand. This need for management becomes increasing important as production levels reach commercial scale levels. This study looked at management practices of several individual harvest crews across an entire harvest season. Data was collected from multiple machines, including balers, shredders, and stackers during the 2013 and 2014 fall harvests. The controller area network (CAN) bus system was utilized to record machine data that was linked to specific GPS coordinates within a given field. The information was then analyzed to identify controllable metrics, such as machine productivity, daily bale production, and bale density. Recognizing these controllable metrics will improve overall logistics as production reaches full scale and reduce overall costs. A techno-economic analysis was executed to quantify cost as performance and quality changed

Productivity and Logistical Analysis of Single-Pass Stover Collection Harvest Systems

A modified biomass combine was used in field experiments focused on measuring the productivity of single-pass bulk harvest and single-pass bale harvest systems. These harvesting machines were outfitted with ISOBUS data loggers to track overall in-field performance data. Testing of machine productivity was conducted at .7 ton/ac (1.6 Mg/ha), 1.5 ton/ac (3.4 Mg/ha), and 2.4 ton/ac (5.4 Mg/ha) for each system. The combine was also tested in a conventional configuration to provide baseline productivity data. Testing revealed significant impacts of the harvesting system on overall machine productivity and highlight the need for additional machine development to support the collection and harvest of biomass residues and grain

Outdoor Storage Characteristics of Single-Pass Large Square Corn Stover Bales in Iowa

Year-round operation of biorefineries can be possible only if the continuous flow of cellulosic biomass is guaranteed. If corn (Zea mays) stover is the primary cellulosic biomass, it is essential to recognize that this feedstock has a short annual harvest window (≤1–2 months) and therefore cost effective storage techniques that preserve feedstock quality must be identified. This study evaluated two outdoor and one indoor storage strategies for corn stover bales in Iowa. High- and low-moisture stover bales were prepared in the fall of 2009, and stored either outdoors with two different types of cover (tarp and breathable film) or within a building for 3 or 9 months. Dry matter loss (DML), changes in moisture and biomass compositions (fiber and ultimate analyses) were determined. DML for bales stored outdoor with tarp and breathable film covers were in the ranges of 5–11 and 14–17%, respectively. More than half of the total DML occurred early during the storage. There were measurable differences in carbon, hydrogen, nitrogen, sulfur, oxygen, cellulose, hemi-cellulose and acid detergent lignin for the different storage treatments, but the changes were small and within a narrow range. For the bale storage treatments investigated, cellulose content increased by as much as 4%s from an initial level of ~41%, hemicellulose content changed by −2 to 1% from ~34%, and acid detergent lignin contents increased by as much as 3% from an initial value of ~5%. Tarp covered bales stored the best in this study, but other methods, such as tube-wrapping, and economics need further investigation

Applying Imidacloprid Via a Precision Banding System to Control Striped Cucumber Beetle (Coleoptera: Chrysomelidae) in Cucurbits

The striped cucumber beetle, Acalymma vittatum (F.) (Coleoptera: Chrysomelidae), is a key pest of cucurbit crops throughout its range. A novel precision band applicator was designed to inject a solid stream of imidacloprid solution in-furrow directly over the seed during planting to reduce beetle leaf feeding on pumpkin, zucchini, and cucumber crops. In 2004 and 2005, bioassays at the cotyledon through fifth leaf were conducted on striped cucumber beetles using seedling leaf tissue grown from seeds treated using both continuous and precision banded in-furrow imidacloprid solution applications. In 2004, 80% of bioassay trials had treatments with beetle mortality significantly higher than the check, whereas 70% of the bioassay trials showed no significant difference in mortality between continuous in-furrow and precision banded treatments. In 2005, 79% of bioassay trials had treatments with beetle mortality significantly higher than the check, whereas 100% of the bioassays showed no significant difference in beetle mortality between continuous in-furrow and precision banded treatments at the same insecticide rate. The environmental savings of precision banded treatments compared with continuous in-furrow treatment reduced imidacloprid up to 84.5% on a per hectare basis for all cucurbits tested in 2004 and 2005, translating into an economic savings up to 030215/ha. In separate bioassay trials conducted in 2005 on pumpkin, where insecticide band length and injection volume were manipulated independently, several treatments had significantly higher beetle mortality than the check. There was a trend of increased beetle mortality in treatments using shorter band lengths combined with higher insecticide solution volumes

Modeling Wireless Signal Transmission Performance Path Loss for ZigBee Communication Protocol in Residential Houses

Low-cost and high performance wireless technologies make it a reality to develop a wireless HVAC control system for multi-zone environmental control in residential houses to improve individual comfort and reduce energy consumption. The lack of understanding on signal transmission performance of wireless sensor network in residential houses limited the application of wireless sensor networks, especially the new ZigBee protocol. This paper is to establish path loss models for predicting wireless data transmission performance in residential houses for ZigBee protocol. Factors affecting the wireless data transmission in residential indoor environment include free space separation, walls, floors, and wireless device inteference. Effects of these factors on the path loss in residential indoor environment were evaluated through empirical testing using received signal strength indicator (RSSI) value measured by commercial ZigBee modules and an embedded microcontroller-based data acquisition system. The model for the effects of walls on the same floor was able to predict 73.6% of the system variability. The measured RSSI data were made versus 1mW transmission source and therefore the RSSI-based path loss models were able to accurately predict the performance of wireless signal of stronger or weaker power transmission systems