Q International Journal of Hydrogen Energy, Vol.2, pp.3140. Pergamon Press, 1977. Printed in Northern ireland LARGE SCALE HYDROGEN PRODUCTION UTILIZING CAR BON IN RENEWABLE RESOURCES*I C. A. ROHRMANN and 3. GREENBORG Battelle-Pacific Northwest Laboratories, Richband, WA 99352, U.S.A. Abstract—By the year 2000 the hydrogen requirements could be met using about one third of available residues. The large and increasing amounts of wastes and residues from agriculture, forestry, other mdustnal and municipal activities are viewed as renewable resources to provide large amounts of hydrogen. In carbon content the current magnitude of such residues exceeds that in the current annual production of all of the coal mined in the U.S. The hydrogen would be produced from these residues by pyrolysis-gasification processes followed by completing the reaction between water and carbon monoxide. The resulting mixture obtainable from oxygen-blown gasiflers is principally hydrogen together with carbon dioxide and water vapor which are readily separated to yield nearly pure hydrogen. A net yield of one pound of hydrogen per five pounds of carbon in the residue is anticipated. Environmental concerns and intensified and expanding agriculture with the development of more effective residue collection and delivery systems assure that residues will be more economical than the conventional carbon resources which are to increase in cost and decline in availability. The demand for hydrogen has been projected to the years 2000 and 2020 at 14 and 50 quads respectively. INTRODUCTION N HYDROGEN, the eleventh most abundant element, comprises 0.127 w% of the earth’s crust, oceans and atmosphere. The greatest amounts of hydrogen exist in the form of water in the oceans and the polar ice caps—about 11% by weight. It also exists in more available forms (but in far less total amounts) in natural gas, crude oil, coal and other organic matter (both living and fossil). A minor amount exists combined in many minerals and rocks. In so far as future large scale availability is concerned, water sources must receive the most attention, since natural gas and other fossil resources clearly have a limited availability and will be exhausted in the foreseeable future. As indicated above, except for the relatively small amount of hydrogen which is combined with carbon in the fossil fuels, essentially all of the world’s hydrogen resource exists as water, primarily in the oceans and polar ice caps. In contrast with its availability as a fuel when bound with the carbon in the fossil resources, all other means of hydrogen use and recovery require that considerable energy be expended to break the bond between the hydrogen and oxygen in water. If hydrogen is to achieve a significant position as a fuel in the industrial, commercial, residential utility, and transportation sectors of the nation’s economy, its production by some means from water will have to be conducted and on a scale which is totally unprecedented in the area of modern chemical processing technology. Today the principal, worldwide use of tounage hydrogen is in the production of anhydrous ammonia, methanol and petroleum refining (gasoline). Most of this production involves carbon in some form, such as natural gas, coal and petroleum. Furthermore, most of this production is accomplished by unique reactions involving carbon with water as either the partial or total source of the hydrogen. Similar reactions may be applied utilizing the carbon in renewable resources such as municipal, agricultural and forestry residues to produce hydrogen. The carbon may also - come from materials grown as an energy feedstock, although this is unlikely due to the intrinsic higher value of food products. The reaction of carbon with water is technically a water splitting cycle wherein hydrogen is released with concurrent preferential carbon oxidation. The resulting carbon dioxide is returned to the atmosphere. Subsequently, the oxygen is released from the carbon dioxide by photosyn- thesis with the carbon fixed concurrently in various organic combinations in the living matter. The cycle is closed (in effect) by solar energy. The process is inherently efficient because no t Presented at 1st World Hydrogen Energy Conference, Miami Beach, Florida, U.S.A., March 1976. • This work was performed by Battelle, Pacific Northwest Laboratories for the Energy Research and Development Administration under contract AT(45-1) 1830. 31 32 LARGE SCALE HYDROGEN PRODUCTION UTILIZING CARBON energy penalty need be taken for the photosynthesis step. In comparison with other water splitting reactions, none are comparable in efficiency, simplicity, and energy economy. Further- more, there is little promise that the other (energy consumptive) water splitting processes will compete favorably with the high efficiency of the electric economy. Thus, there is good reason to concentrate on a hydrogen economy which places emphasis on production from renewable carbon resources and focuses on such hydrogen for meeting the demands for chemical feed stocks, superior storable fuels for transportation and direct heating applications. This energy economy may be described as a scenario which uses hydrogen and electricity independently as the energy vectors. The choice is dependent on the consuming cycle efficiency and the availability of carbon-water cycle hydrogen. The objective of this paper is to project the demand for hydrogen in this economy and estimate the U.S. hydrogen production capability from a carbon-water cycle based on renewable carbonaceous resources which may be recovered from existing food and fiber production efforts. AVAILABILITY AND MAGNITUDE OF CARBONACEOUS RESOURCES The amount of renewable carbonaceous resources has been estimated from various sources and listed in Table 1. An effort has been made to bring these data to a 1975 base. Most of these figures are based on estimates by INMAN [1] and ANDERSON [2]. Data from other sources such as USDA cereal ratios (weight of residue to weight of cereal product) and contacts with industry sources were used to estimate other numbers. It should be emphasized that estimates of quantities and types of residues involve consideration of a system in constant change. For example, municipal wastes can be estimated on the basis of per capita generation; the amount of which is changing with time because of shifts in life styles and consumption patterns. It is generally agreed that the per capita figure is increasing with time. As economic values are recognized for certain wastes they tend to be productively utilized or otherwise consumed instead of being discarded. This shift has been prominent in the wood products industry with residues being recovered for use in the pulp and particle board industries and most recently recovered for TABLE 1. Residues from major U.S. crops (1975) short tons per year Crop Annual short tons of residue Corn 270.600,000 Wheat 108,200,000 Soybeans 37,200.000 Sorghum (grain) 31,500,000 Oats[1] 26,835.000 Barley[1] 20,800.000 Rice (straw and hulls) 7,880,000 Bagause (includes Hawaii) 4,400,000 Cotton (gin trash) 2,300,000 Cotton (other residues)[1] 2,169,000 Peanuts[1] 1,787,000 Sugarbeet pulp[1] 1,679,000 Rye[1] 1,391,000 Sunftower[1] 1,339,000 Tobacco[1] 1,075,000 Estimated total annual 521,380,000 Other major residues Forest residue[2] 163.000.000 Forest products industry residues 120,000,000 Animal Manure (dry)[2] Municipal solid wastes[2] Including sewage solids) 287,000,000 industrial organic 44,000,000 Miscellaneous[2] 50,000,000 Estimated anual total of all U.S. organic wastes = 1,450,000,000 C. A. ROHRMAN AND J. GREENBORG 33 their fuel values. Environmental concerns also influence the trend toward waste utilization. In addition, as a residue is demonstrated to have value, more is sought and used. It is expected that this may also influence the mechanics of harvesting crops to achieve a higher recovery of valuable residues. Thus today, although many crop residues are discarded in the most effective way so as not to impair subsequent crop production, as incentives develop, means will be imposed to improve recovery. Furthermore, as more productive and intensiye agriculture is adopted, an increase in residue production is expected. it is apparent from examination of Table 1 that the origin of these residues is principally from forestry and agriculture. Furthermore most of this material particularly the crop residues is sufficiently dry that additional treatment to minimize moisture content is not required by the contemplated conversion processes. Demands on both the forestry and agricultural industries are directly related to human needs—population. As these needs increase, productivity of these industries must also increase. The production of all such residues can also be expected to increase and very likely will by necessity be more intensively utiuized. CURRENT HYDROGEN PRODUCTION TECHNOLOGY A. Recovery processes 1. Electrolysis. Electrolysis is the most direct means of hydrogen production. However, only where electricity is relatively inexpensive is such a production process practical. Such a process today requires about 24 kW h of electrical energy input per pound of hydrogen produced. Where fuels must be used to produce electricity the overall efficiency of hydrogen production by electrolysis will combine the thermal to electrical efficiency of the fuel burning power plant with the overall efficiency of the electrolysis process itself. Thus the total overall efficiency will be about 25% (35 x 74%) [3]. 2. Carbon-steam. The reaction of steam with hot carbon to produce “blue water gas” and subsequent reaction of the carbon monoxide fraction with more steam to produce more hydrogen was originally the common production process in the absence of the electrolytic process. However in the U.S. it has been replaced by other processes. It was the means for hydrogen production for synthetic ammonia manufacture in the U.S., first in 1927, and continued to be used until after World War II. The chemical reactions are: C+H2O --> CO+H2 CO+H2O --> CO2 +H2 C+2H2O --> C02+2H2 3. Steam reforming of hydrocarbons. The reaction of steam with hydrocarbons under catalytic conditions also yields a gaseous mixture of hydrogen and carbon monoxide. As in the carbon- steam process further reaction of the carbon monoxide with steam increases the yield of hydrogen. This reaction employing methane has been the principal process of hydrogen production in the U;S. since World War II. The chemical reactions are: CH4+H20 --> CO+3H2 CO+H2O --> CO2+H2 CH4+2H2O --> CO2+4H2 4. Steam-iron process. In this largely obsolete process metallic iron is reacted with steam to produce only hydrogen and iron oxide as the products. The iron oxide is regenerated by treatment with a reducing gas such as water gas or producer gas. 5. Partial oxidation. By controlled catalytic oxidation of essentially any hydrocarbon hydrogen is produced. Either air or oxygen combined with steam may be used as the oxidant. This is the second most prevalent means of large scale hydrogen production in the U.S. today. The technique has also been reported to be possible with coal. 6. By product hydrogen Hydrogen is also produced in appreciable amounts as a by-product from other processes such as electrolytic chlorine, petroleum thermal cracking and certain fermenta- tion processes. 34 LARGE SCALE HYDROGEN PRODUCTION UTILIZING CARBON 7. Minor production processes. Although some other processes have been and are still being used for hydrogen production their present impact and importance is relatively minor. Included among these are thermal cracking of methane, methanol reaction with steam, and thermal cracking of ammonia. Review of the above list of processes show that most of them yield all or a large part of the hydrogen by the separation of the hydrogen from the oxygen in water. These may be termed open cycle water splitting processes—open cycle because at least one of the raw materials or regeneration reagents is consumed and largely discarded in another chemical combination, such as carbon to carbon dioxide in the carbon—steam, steam reforming, steam—iron and methanol— steam reactions. B. Thermochemical water splitting closed cycle processes In recent years dozens of closed cycle processes have been proposed and examined [4]. All the raw materials and regeneration reactants in closed cycle processes (except the water and generally the oxygen) are retained in a system of multiple chemical reactions. The energy for promoting the reactions is generally assumed to come either from a high temperature nuclear reactor or from a solar source to avoid dependence on depletable fossil fuel resources. Realization of practical and very inexpensive power from any of these more advanced sources is obviously uncertain in time as well as economics. The major emphasis in the examination of thermochemical water splitting cycles (TCWSC) to date has been to estimate the overall energy efficiency of the total cycle and to determine by small scale laboratory evaluations the chemical feasibility of the cycle reactions. The objective of TCWSC is to provide hydrogen energy at a cost lower than that of competing energy conversion cycles. Theoretically this is possible for some cycles, however, meaningful cost estimates have not yet appeared. The problems of a system of closely integrated multi-chemical processes with refined energy recovery and efficient heat exchange in complex yet practical chemical separation equipment are formidable. If yields no better than those common in modern large scale chemical manufacture are achieved, the likely candidate cycles are reduced to a very few. Jolly [5] emphasized this yield problem from the standpoint of heat efficiency, economics and pollution potential. An extension of Joly’s views on the economics and especially as it relates specifically. to overall process yield is worth emphasizing. Essentially all of these cycles are faced with the seldom acknowledged and yet enormous fundamental problem of materials handling. It should be clear that in order to produce, hydrogen, which is the lightest of elements, by these cycles, elements of much higher atomic (equivalent) weight must be employed. Since compounds rather than the elementsthemselves are involved, the weight relationship is even more impressive, especially when some of the heaviest elements such as uranium are involved. The following cycle, which has been reported as favored [3] by some authorities, exemplifies the problem of materials handling. 3H20+3C12 --> 6HC+ 31202 at 700C 3Fe2O3+l8HCL --> 6FeCl3+9H2O at 650 C 6FeCl3 -. 6FeCl2 + 3Cl2 at 420 C (3) 6FeCl2+8H20 --> 2Fe3O4 + 12HCl + 2H2 at 650 C 2Fe3O4 + 1/202- 3Fe2O3 at 350 C. When the weights of all reactants are added together (except the water and oxygen), and compared with the weight of the desired product, hydrogen, it is shown in Table II that by the above cycle over 940 tons of reactants must be handled to yield one ton of hydrogen, assuming theoretical yields. Furthermore, the materials handling problem becomes almost inconceivable when the practical levels of production which would be encountered when expectations of an “ultimate fuel economy based on hydrogen” are realized. For example, for a 1000 MWe power plant alone, about 1700 tons of hydrogen would be needed as the fuel for each day’s operation. Thus, on the basis of the above favored thermochemical water splitting process, nearly 1.6 million tons of valuable material would need to be handled each day. Furthermore, such processing would have to be done with essentially no losses and at near theoretical conversions in each step in order to assure the minimum level of materials handling. By way of comparison, today’s annual production of each of many common, low-cost industrial chemicals such as potash C. A. ROHRMAN AND 3. GREENBORG 35 TABLE 2. Materials processed and estimated cost of yield losses for a representative closed therinochem- ical water splitting cycle Pounds ot material Amount lost Representative processed per pound at 98% recovery value ot Cost Material ot hydrogen per cycle (Ib) materials, ($/lb) ot losses Cl2 159.57 3.19 0.06 $0.191 Fe2O3 119.78 2.40 0.015 0.036 HO 109.38 2.20 0.03 0.066 FeCl3 243.34 4.87 0.04 0.195 FeC2 193.16 3.86 0.035 0.135 Fe3O4 115.75 2.32 0.015 0.035 940.97 Total 18.84 Total $0.658 pounds lost Raw material value lost per pound ot hydrogen sulfate, titanium dioxide, calcium carbide, borax, sodium silicate, phosphorous, acetone, ethyl alcohol, and carbon disulfide does not exceed 2,000,000 tons. Furthermore to provide even a fraction of the nation’s fuel supply by hydrogen produced in this way certainly hundreds of such plants would have to be operated. The inventory problem of the massive amounts of materials being processed to provide this much hydrogen by these means certainly eliminates all proposed cycles except those based on the most common and most plentiful elements such as iron, chlorine, oxygen and sulfur. In addition an estimate of the cost of yield losses gives another view of the economic problem with this representative cycle as shown in Table 2. Thus yield losses alone for these still relatively inexpensive raw materials could add a cost of over 65 cents per pound to the hydrogen produced in this way. Any efforts at substantially increasing the yield or reducing losses could probably not be justified economically because they would add further to this cost. The situation is not particularly improved when other cycles are considered. For those cycles employing costly raw materials such as iodine, copper, mercury, bromine, vanadium, selenium or uranium the cost imposed by losses amount to very high figures—over one hundred dollars a pound in some cases. It appears reasonable to compare the 65 cent figure as estimated above with the electricity cost for the simple electrolysis process. Earlier it was reported that it required about 24 kWh of electricity to produce a pound of hydrogen by such a process. Thus electricity at a very high price of nearly 2.7 cents/kWh would equal the raw material costs (losses) as estimated above. It is likely that future nuclear, solar, ocean gradient and fusion power costs will be substantially below this figure. Accordingly this view does not provide an encouraging basis for serious consideration of this method of hydrogen production or by other comparable thermochemical water splitting cycles. If the above analysis is examined to review the alternatives, it is clear that multi-cycles with relatively heavy elements amplify the unfavorable situation. Accordingly processes with a very few cycles and employing the lightest elements in the most effective manner should be sought. Carbon is obviously a likely choice. However, this can’t be carbon from fossil sources because of the inevitable and rapid depletion of them. The only alternative is carbon from renewable sources—plant life. The large quantities of organic residues from agriculture, forest products industry and municipal solid wastes are likely sources. Although a dosed cycle is not probable in the usual sense, a carbon based process which returns the carbon as jarbon dioxide for regeneration to “fixed” carbon in plant tissues by natural photosynthesis may be envisioned as a closed cycle on a rather grand scale. C. Hydrogen from renewable carbonaceous resources By essentially present state-of-the-art methods the carbon in carbonaceous residues in the form of wood, tree bark, agricultural field residues, straws, stalks and waste papers can be fairly efficiently used to split, the hydrogen out of water. It is only necessary to pyrolyze such residues at 36 LARGE SCALE HYDROGEN PRODUCTION UTILIZING CARBON only moderately high temperature and atmospheric pressure in the presence of oxygen and water vapor to promote the following common basic reactions: C+H20 --> CO+H2 (at 700 C) CO + H20 --> CO2 + H2 (at 250-500C) (4) C+2H20 --> CO2+2H2 Assuming theoretical yields and conversions, for the reactions as shown here only three pounds of carbon are required to produce one pound of hydrogen. Thus, such a cycle is from a few hundred to about 1000 times less burdensome from a materials handling standpoint than any proposed thermochemical cycle and in addition is far less complex from a processing standpoint. Furthermore the reactions are so well known that no laboratory research is needed to define the chemistry, thermodynamics, or ezonomics. These reactions can be made to proceed successively without interruption for intermediate processing, composition adjustment or introduction of different raw materials. Because of the low cost of the raw material and lack of environmental concerns for the vented carbon dioxide, the necessity for very high yields in the process does not exist. An overall yield of 60 percent would be expected with most of the loss being the use of the residues as the source of energy to promote the overall reaction which is endothermic. By applying the yield-cost estimate as above for representative closed cycle, the results are obtained as shown in Table 3. The total raw material cost per pound of hydrogen is thus shown to be $0.10. At this value the electricity to match this cost for simple electrolysis of water would have to be as low as about $0.OO4/kWh. This is about equal to the cheapest hydro power produxd in the U.S. today and is not likely to be matched by any alternative power supplies in the future. Thus whereas for hydrogen production the more favorable closed thermochemical water splitting cycles on the basis of material costs alone are indicated to be uncompetetive with simple electrolysis of water at today’s power costs, the thermochemical processing of carbonaceous resources via pyrolysis- gasification is shown to be very likely competitive with today’s power costs for the conventional electrolysis process. It can be shown that essentially all of the dry residues listed in Table 1 have a carbon content of not less than 40% by weight, which is about the same as that of lignite as mined. For comparison the average carbon content of U.S. bituminous coal is about 70% (and may range from 55 to 85%). In recent years coal production in the U.S. has amounted to close to 600,000,000 or 420,000,000 tons of carbon. On the basis of these figures the carbon content of these annual amounts of residues exceed that in the annual amount of coal mined in the U.S. Energy value of fuels and residues may be compared as follows: Imported natural gas in 1980 may be valued at about $2.50/million Btu. Delivered off-shore oil is now about $15/barrel or about 2.65/million Btu. Coal delivered at $30/ton provides energy at about $12 per million Btu. Dry residues delivered to a processing facility with a heat content of about 6500 Btu/lb (and at 40% carbon) should therefore have a value of about half that of coal of $15/ton or $1.15/million Btu. It is likely that the delivered cost of some residues, such as municipal solid wastes, does not exceed this value today. Furthermore improvements in existing collecting equipment appear reasonable and likely to broaden very considerably the low cost collectability of the other residues, including the important ceieal straws. Others have given serious consideration to the “energy plantation” concept for cultivating plant material- for its fuel as weil as carbon value [6,7]. The efficient utilization of the carbon in existing agricultural residues in the near future may accomplish the objectives defined for the TABLE 3. Estimated material cost of a residue gasification process for hydrogen production Value lbs of of such Total carbon processed carbon cost of Material per pound of hydrogen Loss ($/lb) raw material Carbon (already 0.02 $0.10 (in residue) included) C. A. ROHRMAN AND J. GREENBORO 37 energy plantations. Prospects for productive realization in a relatively short length of time are very favorable. HYDROGEN ENERGY DEMAND The 1972 Department of the Interior energy demand study, “United States Energy through the Year 2000”, predicts a 4% annual energy demand growth rate to 192 quads (1015 Btu/quad) by year 2000; 28.8% supplied by nuclear and hydro power, the remaining 71.2% supplied from fossil resources. Since 1972 circumstances have developed which should significantly alter this prediction: The price of fossil fuels has more than tripled, petroleum, and to some extent, natural gas is no longer distributed under free market conditions, and national efforts in conservation, solar, geothermal and fusion energy have been intensified. For this study the DOI prediction has been changed as follows to develop the hydrogen/electric model shown in Fig. 1. 182.3 FIG. 1. Hydrogen/electric energy economy—annual consumption by source, 1975-2020. Energy demand growth rate was reduced from 4 to 2%. Energy demand was extrapolated to year 2020 based on continued 2% growth rate. (Total U.S. energy production has grown at a relatively constant rate of 2.7%/year since 1900 [8]; the rate since 1960 has exceeded 4%.) Growth in the electric energy fraction of the DOI prediction was unchanged. This in effect reduced the annual growth rate of electric energy production from 5.2 to 3.2%. The DOI model calls for 31% of the electrical source energy to originate as fossil fuels. It is assumed that a portion of this energy will be supplied by solar and geothermal sources; 40% by year 2000, 90% by year 2020. It is assumed that hydrogen is substituted for non-electric fossil fuel demand as follows: 20% in year 2000 50% in year 2020. The above analysis predicts that the hydrogen demand will be 14 and 50 quads, respectively, in the year 2000 and 2020. This, of course, assumes the key incentive of cost competitive hydrogen supply which is provided by the high conversion efficiency of the carbon cycle. - HYDROGEN ENERGY SUPPLY FROM RENEWABLE CARBONACEOUS RESIDUES Current residues (1,450,000,000 tons/yr) could produce 14 quads/yr of hydrogen if all residues were collected and used for that purpose. The hydrogen energy demand model predicts a hydrogen demand of 14 quads in year 2000 and 50 quads in year 2020. There are several bases for predicting the future availability of residues. They are: 1. Assume residues are proportional to growth of population. (Historically 1.34%; over the last several years slightly less than 1%.) 38 LARGE SCALE HYDROGEN PRODUCTION UTILIZING CARBON 2. Assume residues are proportional to growth of the GNP. (Historic GNP growth rate is 4.25%; growth rate averaged over the last 5 years has been 2%—strongly influenced by the oil embargo and recession.) The growth of residues is anticipated to follow growth in GNP, however, GNP growth has been reduced to 3.2% to adjust for lower population growth (1.0 vs 1.34%) a result of significant and effective population control efforts. Principal residues are proportional to GNP growth, however, agricultural residues should exceed significantly GNP growth since the U.S. is continuously providing an increasing share of the world’s food supply. Thus, there is excellent opportunity to utilize the increase in agricultural residues. Agricultural residue fuel yield and value is expected to influence crop choice and development increasingly over the near future, although we see little possibility for energy crops grown at the expense of food crops. The current U.S. availability of carbonaceous residues may be converted to hydrogen by the following relationship: Hydrogen = (0.4)(1.45 x 10'9 tons residue)(2000)(60941 Btu/lb H2) = 14.14 (quads) (5 lb C/lb H2)(10’15 Btu/quad) Thus from today’s residues a total of 14 quads of hydrogen could be produced. It should be noted that this is essentially equal to projected demand for hydrogen in the year 2000. If it is assumed that agricultural residues increase annually at a 4% rate and all other residues at the rate equal to the rate for the GNP or 3.2%, it is estimated that a total of 3,686,000,000 tons of residues may be available in the year 2000 and 8,085,000,000 tons in the year 2020. It is realized that it is not practical to collect all available residues. As conventional carbon resources increase in price and decrease in availability, a greater fraction of the renewable resources would expect to be utilized. By the year 2000 only 40% need be collected and by 2020, 65% to meet projected hydrogen demands. Esimated costs and feasibility of collection of agricultural field residues It is not the intent of this paper to present extensive details of anticipated economics and feasibility of the collection and delivery of agricultural field residues; however, it is felt justified to at least touch upon these extremely important factors especially in the light of the current equipment capabilities which may not be generally known to those.with a more scientific interest in the problem of residue conversion. A limited review of agricultural machinery manufacturers* shows an impressive variety of high-capacity, low-labor equipment for efficient on-site pick-up and accumulation of hay, forage, fodder, and field residues. Manufacturers also offer large capacity equipment for stack pick-up and highway hauling. Manufacturer’s brochures show field-to-roadside pick-up and delivery equipment in eight-ton capacities with claims of a hundred tons per day (8 hr) with only one operator. Equipment for pick-up and rapid highway movement of fifteen-ton stacks is also available. All of these systems are for field pick-up and delivery of loose residues or- crop material with no need for bailing or other means of compaction or densification. Reports on the integrated systems and costs for such field collection plus highway delivery generally applicable to field residues have not been noted; however, data on segments of such systems for specific residues which are available provide a reasonable basis for indicating likely costs. For example, details presented in the “Report of the First World Straw Conference” [9] and in reference 10 provide applicable cost data. The full cost for pick-up and roadside placement - - (stacking) of grass seed industry straw in Oregon is reported to be in the range of 5—$6/ton. The cost of highway delivery of another residue is reported to be 6 cents/ton per mile. Thus, on the basis of these data, the total cost for pick-up and delivery to a processor at a distance of twenty-five miles should not exceed about $8/ton. However, this does not include any credit to the owner of the residue. Although in many cases it is desirable to remove and dispose of the residue, it would be reasonable to assume some charge for it, if it is found to be of value as a raw material in a process Qfl which a profit can be shown. In view of this likelihood, some modest value or credit of say four or five dollars a ton should be assumed. Then the total delivered cost of residues can be * Names such as Deere, Hesston, Farmhand Gehl and McKee arc among these. C. A. ROHRMAN AND J. GREENBORG 39 assumed to be around twelve dollars per ton. This should be the case for most seed crops such as corn, grain, rice, soy beans, etc. which comprise the major potentially useful residues and should be dry enough to require no further treatment for the gasification process. It should be noted that this figure is below the fifteen dollar figure mentioned earlier to arrive at the cost of $1.15/million Btu energy value of such residues. The above details support the view that field residues and other carbonaceous wastes can be expected to be made available at costs sufficiently reasonable to justify their serious consideration for productive uses such as for large-scale hydrogen production. It has been advanced by some that removal of agricultural field residues is counter-productive. They suggest that such practices remove residues which serve as an erosion control material and soil conditioner in the form of humus as well as return to the soil mineral nutrients such as potash and phosphorus. There are strong counter arguments. More of the nutrients are removed in the food product than in the straw (particularly for the cereals). For these, replacement (fertilization) is already required as accepted agricultural practice. This is particularly so in the case of nitrogen. Under many conditions, the incorporation of residues back into the soil requires the addition of additional nutrients to promote the biological decomposition of these wastes (to humus) without which a net loss of nutrient is realized (because of the nutrient demands of organisms involved in the decomposition process). As agricultural production is intensified the problem of pest control is also magnified. It has been well documented that remaining concentra- tions of agricultural field residues provide improved conditions for carry over of objectionable insect and disease populations. Thus under more intensified agriculture, the removal of residues may become an accepted and possibly a necessary practice. CONCLUSIONS The demand for hydrogen is expected to be 14 quads in the year 2000 and 50 quads in 2020. On the basis of today’s estimates of the availability of renewable carbonaceous resources and projected growth in these quantities, only 40% of these need to be processed in 2000 and 65% in 2020 to provide the amounts of hydrogen. Such processing will be via pyrolysis-gasification conversion technology which is essentially present state-of-the-art and thus needs no major research program to achieve significant productive results in the near future. Except for some relatively minor sources such as the by-product from chlorine production via electrolysis of brine, essentially all hydrogen production today is based on the use of some carbon resource such as natural gas, petroleum, and coal. On the expectation that these conventional carbon resources (particularly gas and petroleum) will decline in availability and continue to increase in price, economic energy from other sources must be depended on for hydrogen production. Such energy may also be from geothermal, solar, or breeder and fusion reactors. Each of these potential sources have severe problems in economics, as well as technology, such that early relization of practical power is not anticipated. In comparison with these developing resources, the early realization of practical conversion of renewable carbonaceous resources to hydrogen appears highly favorable. Because of the magnitude of resource processing require- ments, economics and specifically the very unlikely realization of required yields, the closed cycle thermochemical water splitting processes do not appear favorable in comparison. Although the proposed concept of utilizing renewable carbonaceous residues may be adequate to provide the needs for hydrogen in the indicated time frame, these resources cannot be expected to provide much additional energy or carbon for alternative uses. However, this assumes no major advances in culture and harvesting, a situation which in view of the major progress in the last fifty years is wholly unrealistic, it is reasonable to expect that where plant - breeding and agronomy research has been so successful in increasing productivity of seed, fiber, - and oil crops, similar research can be expected to yield major increases in by-product field residues if these are needed as they appear to be for production of essential products other than hydrogen such as methanol, gasoline, urea, and the whole spectrum of vital chemical products presently obtained from the conventional carbon resources. Acceptable economics for residue collection and delivery appear to be attainable by systematic utilization of existing efficient and low-labor farm machinery. - The growth in renewable carbonaceous residue availability is not expected to be less than the 40 LARGE SCALE HYDROGEN PRODUCIION UTILIZING CARBON growth of the Gross National Product and in the case of residues from agriculture for food production is expected to grow at a rate exceeding those of the GNP. REFERENCES 1. R. E. INMAN data (NES Grant GI 43863) Stanford Research Institute (1975). 2. L. L. ANDERSON USBM Information Circular 8549: Energy potential from organic wastes: A review of the Quantities and Sources (with some adjustments by the present authors.) 3. Hydrogen and other synthetic fuels: A Summary of the Work of Synethetic Fuels Panel for the Federal Council on Science and Technology, September (1972). 4. R. E. CRAO, Thermochemical water decomposition processes, Ind. Eng. Chem. Prod. Res. Develop. 13, 94—101 (1974). 5. F. JOLY, Economic criteria of selection for closed-cycle thermochemical water-splitting processes. The Hydrogen Economy Miami Energy Conference, Miami, Florida, 17—20 March (1974). 6. G. C. Szego & C. C. KEMP, Energy forests and fuel plantations, Chem Tech 275—281, May (1973). 7. D. L. KIASs, A perpetual methane economy—is its possible?, Chem Tech 161—168, March (1974). 8. R. P. OMBERO et al., The incentive for the liquid metal fast breeder reactor—A revised economic analysis, Hanford Engineering Development Laboratory, Richland, Washington, December (1975). 9. T. R. Miles, Report of the 1st World Straw Conference, Eugene, Oregon, May 1975, and Oregon Field Sanitation- Committee—Status of Projects, 17 February (1976). 10. C. R. ENGL.ER et al., Appendix A, the potential of manure pyrolysis for ammonia production and electric power generation in Kansas, September 1974, Institute for Systems Design and Optimization, Kansas State University, Manhattan, Kansas.

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