102,951 research outputs found
Sustainability of Corn Stover Harvest for Biomass
No full textOff-farm demand for crop residues is expected to grow as bioenergy policies become effective. Demand for residues will provide farmers with an additional source of revenue but it may also trigger losses in soil organic carbon and increases in fertilizer application. This study develops a dynamic economic model of stover harvest that permits conceptualization and quantification of these potential tradeoffs. We parameterize our model based on publicly available studies of soil biophysical relationships in the Corn Belt. Under these parameter values and 2010 corn and fertilizer prices harvesting stover is not economically convenient at prices below $53 per dry ton of stover. Results suggest that the rate of stover harvest may be quite sensitive and negatively linked to corn prices, which means that policies favoring the use of stover for biomass may be overridden by further increases in corn price. The negative link between stover harvest and corn prices, while somewhat counterintuitive, is driven by the fact that removal of stover reduces future grain yield (through reductions in soil organic carbon). Results also seem to indicate that, under plausible parameter values, profit maximizing farmers would increase stover supply in response to increases in stover price. However increases in supply are, according to our simulations, associated with (potentially significant) reductions in soil organic carbon (and hence carbon emissions as these are positively linked) and increases in nitrogen application (and potential runoffs). This result suggests that concerns about adverse environmental implications of harvesting stover may be justified, and more precise quantification of environmental tradeoffs should be pursued by future research.stover supply, biomass, soil productivity, soil organic carbon, nitrogen, Environmental Economics and Policy, Farm Management, Land Economics/Use, Resource /Energy Economics and Policy, C61, Q12, Q24, Q42, Q53,
A Corn Stover Supply Logistics System
No full textPublished in Applied Engineering in Agriculture, Vol. 26(3): 455‐461, 2010. American Society of Agricultural and Biological EngineersCorn stover, Economics, GHG emission, Logistics, Roll press compaction, Tub grinding, Agribusiness, Crop Production/Industries,
The Viability of Harvesting Corn Cobs and Stover for Biofuel Production in North Dakota
No full textThis study examines the impact of stochastic harvest field time, corn cob and stover harvest technologies, increases in farm size, and alternative tillage practices on profit maximizing potential of corn cob and stover collection in North Dakota. Using three mathematical programming models, we analyze farmers’ harvest activities under 1) corn grain only harvest option, 2) simultaneous corn grain and cob harvest(one-pass) option 3) separate corn grain and stover harvest (two-pass) option. Under the first corn grain only option, farmers are able to complete harvesting corn grain and achieve maximum net income in a fairly short amount of time with existing combine technology. However, under the simultaneous corn grain and cob one-pass harvest option, our findings indicate that farmers generate lower net income as compared to the net income of corn grain only harvest option. This is due to the slowdown in combine harvest capacity as a consequence of attaching cob harvester to the back of combine. Under the third option of a two-pass harvest system, time allocation is the main challenge and our evidence shows that with limited harvest field time available, farmers find it optimal to allocate most of their time harvesting grain, and then proceed to bale stover if time permits at the end of harvest season. As farm size increases, farmers are especially challenged in finding time to harvest both corn grain and cobs/stover. We show that a small decrease in corn yield due to changes in tillage practice can result in a large decline in the net profit of harvesting corn grain and cobs/stover.Cob, Stover, harvest field time, optimization, farm size, tillage, Crop Production/Industries, Production Economics,
Effect of biological pretreatment with Trametes hirsuta yj9 on enzymatic hydrolysis of corn stover
No full textIn this study, a newly isolated Trametes hirsuta yj9 was used to pretreat corn stover in order to enhance enzymatic digestibility. T. hirsuta yj9 preferentially degraded lignin to be as high as 71.49% after 42-day pretreatment. Laccase and xylanase was the major ligninolytic and hydrolytic enzyme, respectively and filter paper activity (FPA) increased gradually with prolonged pretreatment time. Sugar yields increased significantly after pretreatment with T. hirsuta yj9, reaching an enzymatic digestibility of 73.99% after 42 days of pretreatment. Scanning electron microscopy (SEM) showed significant structural changes in pretreated corn stover, the surface of pretreated corn stover became increasingly coarse, the gaps between cellulose fibers were visible, and many pores were developed. Correlation analysis showed that sugar yields were inversely proportional to the lignin contents, less related to cellulose and hemicellulose contents. (C) 2011 Elsevier Ltd. All rights reserved
Improved hydrogen production via thermophilic fermentation of corn stover by microwave-assisted acid pretreatment
No full textA microwave-assisted acid pretreatment (MAP) strategy has been developed to enhance hydrogen production via thermophilic fermentation of corn stover. Pretreatment of corn stover by combining microwave irradiation and acidification resulted in the increased release of soluble substances and made the corn stover more accessible to microorganisms when compared to thermal acid pretreatment (TAP). MAP showed obvious advantages in short duration and high efficiency of lignocellulosic hydrolysis. Analysis of the particle size and specific surface area of corn stover as well as observation of its cellular microstructure were used to elucidate the enhancement mechanism of the hydrolysis process by microwave assistance. The cumulative hydrogen volume reached 182.2 ml when corn stover was pretreated by MAP with 0.3 N H(2)SO(4) for 45 mm, and the corresponding hydrogen yield reached 1.53 mol H(2)/mol-glucose equivalents converted to organic end products. The present work demonstrates that MAP has potential to enhance the bioconversion efficiency of lignocellulosic waste to renewable biofuel. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved
Corn Stover Potential: Recasting the Corn Sweetener Industry
No full textCorn stover is by far the largest single available biomass not being used, representing more than one-third of the total waste, including municipal solids. An estimated 200 million dry tonnes (t) remain each year as aboveground residue. THE CORN STOVER ISSUE The corn sweetener industry is based on processing corn grain (maize), creating value-added products such as glucose, dextrose, and fructose. Conversion of corn stover to sugars has been stymied for years due to cost. Environmental benefits, wider adaptation of sustainable farming practices and the relentless improve-ments in biotechnology are expected to overcome the economic hurdle within the next five years and recast the corn sweetener industry. The corn stover industry uses about 8 % of the corn crop (20 million t) in 1997; the fuel ethanol industry used about 13 million t (515 million bu). These combined demands equal 13 % of domestic demand for corn. Corn stover consists of the stalks, leaves, and cobs remaining aboveground after the corn kernels are harvested. About 1 kg of stover is produced per kg of grain. In 1997 about 200 million dry t of stover was produced. The mass of stover increases with the yield of the corn-expected to increase 1 % to 2 % annually More than 90 % of the stover is left in the fields. Less than 1 % of corn stover is collected for industria
Effects of ammonia fiber expansion (AFEX) treated corn stover on anaerobic microbes and corresponding digestion performance
No full textDynamic changes in microbial communities and digestion performance of AFEX treated corn stover co-digestion were compared to untreated corn stover co-digestion. Even though it took longer to stabilize the AFEX treated corn stover co-digestion system than it did for the untreated corn stover co-digestion, the results show that AFEX treated corn stover is a good feedstock to enhance the archaea community and improve biogas production. In the stabilized digestion system, the AFEX treated corn stover co-digestion increased abundance of archaea community (11.8%) by approximately three times compared to the untreated corn stover co-digestion (4.3%), The corresponding biogas production (213 L/kg VS loading) of the AFEX treated corn stover co-digestion was 22% higher than that (175 L/kg VS loading) of the untreated corn stover co-digestion. AFEX treatment could enable more extensive use of lignocellulosic biomass for anaerobic digestion to generate biogas and thereby provide another route for lignocellulosic biofuel production
Using Real Options to Evaluate Investments in Ethanol Facilities
No full textThis paper uses real option analysis to evaluate investment decisions in ethanol facilities. First, we consider the option to expand the scale of a conventional ethanol plant. Second, we evaluate the option to choose a production technology given three drymilling choices – a conventional natural gas-fueled plant, a stover-fueled plant, and a stover-plus-syrup-fueled plant. We develop input-output coefficients and annual cash flow projections for a hypothetical small ethanol plant (50 million gallon capacity) using available industry and market price data. Scenario analysis is done to evaluate the effect of profitability and volatility on the option to expand. We find that the best decision during 2001-07 is often to expand, since the net present values of the investment project are positive. However, there are states in the binomial tree where it is best to wait. In relatively few such states the expansion project is simply rejected. During the early part of the period low profitability and high volatility more frequently favor strategies of waiting to invest until prices and profitability improve. During the latter part of the period (2005-07), profitability is sharply higher and most often the best strategy is to invest in the expansion. This result is consistent with the observed rapid increase in industry production capacity during 2005- 07. However, more recent market developments, sharply higher corn and natural gas prices and slightly higher ethanol prices during late 2007-early 2008, have combined to sharply reduce expected plant cash flow and profitability and cash flow volatility. The implication is that plant investment plans in 2008 would be increasingly placed on hold, which the real option model correctly predicts. The real option analysis of technology choice indicates that the stover-fueled technologies are most often chosen when compared to a natural gas-fueled conventional technology based on the prices that existed during 2001-2007.Financial Economics, Resource /Energy Economics and Policy,
Energy Crop Production Costs and Breakeven Prices Under Minnesota Conditions
No full textProduction costs and breakeven prices were calculated for four energy crops plus corn stover. The energy crop breakeven prices were calculated under two different scenarios regarding land costs and the opportunity costs of not utilizing the land for some other competing land use. One scenario is that the competing land use is pasture. The other is that the energy crops would compete with grain crops on more expensive land, and would need to provide a return over land costs equal to returns on the grain crops. Corn stover would be the cheapest of the energy biomass sources considered, at 77/ton of dry matter. A grassland crop under low fertilization with a 2-ton yield but a longer stand life has the highest cost at 81/ton. Willow is at an early stage of development in Minnesota, but it would be the cheapest energy crop at 40/acre. The more expensive grain crop land translates directly into higher energy crop breakeven prices which are also presented in the paper.Crop Production/Industries,
A Corn Stover Supply Logistics System
No full textWe evaluated the economics, energy inputs, and greenhouse gas (GHG) emissions for a proposed “field to facility”
corn stover logistics system. The system included collection and transport by round bales to local storages within 3.2 km
(2 mile) of the field during the fall harvest period followed by processing at the local storage sites throughout the year using
mobile units which converted the bales to bulk material by tub‐grinding and roll‐press compacting to 240 kg/m3 (15 lb/ft3)
to achieve 22.7‐t (25‐ton) loads for truck delivery to an end user within a 48‐km (30‐mile) radius. The total cost and fossil
energy consumption for delivering the bulk corn stover (15% moisture) to end users were 74/ton) and 936 MJ/t,
respectively. The total fossil energy consumption was equivalent to approximately 7% of the energy content of corn stover.
The life‐cycle GHG emission for heat and power applications was approximately 114 kg CO2e/t at 15% moisture or
8 g CO2e/MJ of dry matter including emissions for logistics and combustion, but excluding those associated with soil organic
carbon (SOC) loss. Our estimates show that as a fuel for heat and power applications, corn stover reduced life‐cycle GHG
emissions by factors of approximately 8 and 14 compared to natural gas and coal, respectively
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