Agriculture is now a petrochemical industry
One can see from the data below that biomass is already the largest renewable solar derived energy source in the USA. All of these potential biomass sources compete for land. Some of them are not net energy producers. None of them have the conversion efficiency attained by advanced algae culture. None of the existing sources can co-exist with urban expansion (which is unavoidable due to population growth). Only roof level Phytotechnology has the potential to harness the photosynthesis process without land-use limitation. The Sola Roof is a very high producer of net energy/food/water and will result in energy conservation and distributed production and use of these resources. In support of these statements please read below:
In reference to the ability of the natural or cultured forest or agricultural crops to provide net energy you can refer to:
http://www.dieoff.com/page84.htm Titled:"Renewable Energy: Economic and Environmental Issues", by David Pimentel, G. Rodrigues, T. Wane, R. Abrams, K. Goldberg, H. Staecker, E. Ma, L. Brueckner, L. Trovato, C. Chow, U. Govindarajulu, and S. Boerke. (Originally published in BioScience -- Vol. 44, No. 8, September 1994)
Here are some extracts from the article above:
A city of 100,000 people using the biomass from a sustainable forest (3 tons/ha) for fuel would require approximately 220,000 ha of forest area, based on an electrical demand of 1 billion kWh (860 x 109 kcal = 1 kWh) per year (Table 2). Nearly 70% of the heat energy produced from burning biomass is lost in the conversion into electricity, similar to losses experienced in coal fired plants. The area required is about the same as that currently used by 100,000 people for food production, housing, industry, and roadways (USDA 1992).
The burning of biomass is environmentally more polluting than gas but less polluting than coal. Biomass combustion releases more than 100 different chemical pollutants into the atmosphere (Alfheim and Ramdahl 1986). Wood smoke is reported to contain pollutants known to cause bronchitis, emphysema, and other illnesses. These pollutants include up to 14 carcinogens, 4 cocarcinogens, 6 toxins that damage cilia, and additional mucus-coagulating agents (Alfheim and Ramdahl 1986, DOE 1980). Because of pollutants, several communities (including Aspen, Colorado) have banned the burning of wood for heating homes. When biomass is burned continuously in the home for heating, its pollutants can be a threat to human health (Lipfert et al. 1988, Smith 1987b).
When biomass in the form of harvested crop residues is used for fuel, the soil is exposed to intense erosion by wind and water (Pimentel et al. 1984). In addition to the serious degradation of valuable agricultural land, the practice of burning crop residues as a fuel removes essential nutrients from the land and requires the application of costly fossil-based fertilizers if yields are to be maintained. However, the soil organic matter, soil biota, and water-holding capacity of the soil cannot be replaced by applying fertilizers. Therefore, we conclude that crop residues should not be removed from the land for a fuel source (Pimentel 1992).
Biomass will continue to be a valuable renewable energy resource in the future, but its expansion will be greatly limited. Its use conflicts with the needs of agricultural and forestry production and contributes to major environmental problems.
Ethanol: A wide variety of starch and sugar crops, food processing wastes, and woody materials (Lynd et al. 1991) have been evaluated as raw materials for ethanol production. In the United States, corn appears to be the most feasible biomass feedstock in terms of availability and technology (Pimentel 1991).
The major energy input in ethanol production, approximately 40% overall, is fuel needed to run the distillation process (Pimentel 1991). This fossil energy input contributes to a negative energy balance and atmospheric pollution. In the production process, special membranes can separate the ethanol from the so-called beer produced by fermentation. The most promising systems rely on distillation to bring the ethanol concentration up to 90%, and selective-membrane processes are used to further raise the ethanol concentration to 99.5% (Maeda and Kai 1991). The energy input for this upgrading is approximately 1280 kcal/liter. In laboratory tests, the total input for producing a liter of ethanol can potentially be reduced from 10,200 to 6200 kcal by using membranes, but even then the energy balance remains negative.
Any benefits from ethanol production, including the corn by-products, are negated by the environmental pollution costs incurred from ethanol production (Pimentel 1991). Intensive corn production in the United States causes serious soil erosion and also requires the further draw-down of groundwater resources. Another environmental problem is caused by the large quantity of stillage or effluent produced. During the fermentation process approximately 13 liters of sewage effluent is produced and placed in the sewage system for each liter of ethanol produced.
Methanol: Methanol is another potential fuel for internal combustion engines (Kohl 1990). Various raw materials can be used for methanol production, including natural gas, coal, wood, and municipal solid wastes. At present, the primary source of methanol is natural gas. The major limitation in using biomass for methanol production is the enormous quantities needed for a plant with suitable economies of scale. A suitably large methanol plant would require at least 1250 tons of dry biomass per day for processing (ACTI 1983). More than 150,000 ha of forest would be needed to supply one plant. Biomass generally is not available in such enormous quantities from extensive forests and at acceptable prices (ACTI 1983).
If methanol from biomass (33 quads) were used as a substitute for oil in the United States, from 250 to 430 million ha of land would be needed to supply the raw material. This land area is greater than the 162 million ha of US cropland now in production (USDA 1992). Although methanol production from biomass may be impractical because of the enormous size of the conversion plants (Kohl 1990), it is significantly more efficient than the ethanol production system based on both energy output and economics (Kohl 1990).
Compared to gasoline and diesel fuel, both methanol and ethanol reduce the amount of carbon monoxide and sulfur oxide pollutants produced, however both contribute other major air pollutants such as aldehydes and alcohol. Air pollutants from these fuels worsen the tropospheric ozone problem because of the emissions of nitrogen oxides from the richer mixtures used in the combustion engines (Sillman and Samson 1990).
Solar energy technologies, most of which require land for collection and production, will compete with agriculture and forestry in the United States and worldwide (Table 2). Therefore, the availability of land is projected to be a limiting factor in the development of solar energy. In the light of this constraint, an optimistic projection is that the current level of nearly 7 quads of solar energy collected and used annually in the United States could be increased to approximately 37 quads (Ogden and Williams 1989, Pimentel et al. 1984). This higher level represents only 43% of the 86 quads of total energy currently consumed in the United States (Tables 1 and 3). Producing 37 quads with solar technologies would require approximately 173 million ha, or nearly 20% of US land area (Table 3). At present this amount of land is available, but it may become unavailable due to future population growth and increased resource consumption. If land continues to be available, the amounts of solar energy (including hydropower and wind) that could be produced by the year 2050 are projected to be: 5 quads from biomass, 4 quads from hydropower, 8 quads from wind power, 6 quads from solar thermal systems, 6 quads from passive and active solar heating, and 8 quads from photovoltaics (Table 3).
It is imperative to develop a sustainable alternative to agro-industry because - just like the oil industry - it is an exploitation industry that is moving into its resource depletion phase - running out of the natural reserves of "good earth" and aquifers that were created over the past millennia by a healthy ecosystem.