Food and Water
In this section, we examine several methods for high density farming. In generally, intensive food production saves land and water, at the cost of additional energy input.
Greenhouses are an increasingly widely used tool for producing vegetables . Greenhouses are estimated to have the following environmental impacts relative to outdoor farming, often spending more energy to save land and water.
Following is an illustration of the energy required to produce all world tomatoes from greenhouses.
Greenhouses can be used to grains, such as barley , but the environmental case for doing so may be weaker than it is for vegetables.
The Netherlands is the world leader in effective use of greenhouses. They have drastically cut water and pesticide usage, and the Netherlands, a country that is not naturally well-suited for agriculture, is the number two food exporter by monetary value.
Hydroponics--the practice of growing plants with a nutrient solution instead of soil--may also save land and water at the cost of greater energy consumption. The following impacts, relative to open field farming, have been estimated.
Over 80% of the energy consumption identified by Barbosa et al.  is for heating and cooling, an area for which a clean source of low-temperature industrial heat would be valuable. Passive ventilation  and efficient LED lighting  would also save energy.
Related growing techniques are aquaponics, which is a symbiotic combination of an aquaculture and hydroponic system, and aeroponics, which does not use a growing medium. Their water, fertilizer, and land use impacts have been estimated as follows.
An aquaponics system can save fertilizer consumption by using excretion from the fish .
Vertical farming is the concept of growing food in layers. This may refer to the food-producing skyscrapers described by Dickson Despommier , or more commonly, any indoor growing that relies mostly on artificial lighting . Even more so than greenhouses, vertical farm conserves land and water at the cost of additional energy consumption.
Most of the energy cost of a vertical farm is for artificial lighting, and vertical farms also have higher labor costs per unit product than other forms of farming . Due to high energy and other costs, vertical farms for the foreseeable future will probably be confined to producing leafy greens, herbs, and berries, which together constitute 6% of global caloric intake .
Cellular agriculture refers to the cultivation of single-celled organisms for food. In some form, cellular agriculture goes back centuries in the cultivation of yeast and algae. Expanded use of new techniques could radically transform food production.
Today, single-cell organisms are typically grown from agricultural residue, thus inheriting the environmental impacts of conventional farming. Even so, expanded use of such organisms could reduce impacts.
If electrolytically produced inputs, such as hydrogen, methanol, and ammonia, are used, most land use can be saved with single-cell organisms, but at the cost of very high energy input.
At 25 kWh per kg crop, replacing all cereal and soy crops  in the world would require about 83 petawatt-hours of electricity each year, or triple current world production . At 5¢/kWh, electricity costs alone are $1.25 per kilogram of food, well in excess of the 30-40¢/kg price recently observed for soybeans .
Algaculture is the cultivation of algae for food, fuel, or other purposes. Today algaculture is used primarily for high value applications, such as nutritional supplements and food additives . There is particular interest in algae as animal feed .
Algaculture typically has a much higher yield that conventional farming.
The highest yielding algaculture systems require a carbon dioxide source in greater concentration than is available in the atmosphere , which can be achieved by direct air capture or colocation with an emissions source.
Cultured meat, also called in vitro meat or synthetic meat, is grown in a reactor from animal muscle cells. Aside from the cells that are used to begin the growth process, cultured meat is never part of a living animal.
As with other forms of intensive food production, cultured meat is likely to save land at the cost of greater energy input. The following are estimated impacts of common meats, cultured meat, and other meat alternatives.
Cultured meat is still not a commercial product, and consumer acceptance is uncertain . Additionally, the reliance on fetal bovine serum and other animal products for cell culturing may be problematic for those who avoid meat for animal welfare concerns, though alternatives to animal products for growth media are active areas of research .
While some intensive farming methods are widely used today, such as greenhouses, radical intensification of agriculture, such as through vertical farming, power-to-food, or cultured meat, requires a prohibitive level of energy consumption. Developing abundant, low-impact, and low-cost energy sources may thus have the benefit of sparing large swathes of land from food cultivation.
New agricultural technologies, such as aquaculture, have historically been commercialized through a constellation of programs including publicly funded research and development, extension services to connect farmers with new research, crop insurance, federal loans, environmental and conservation assistance, and marketing services . Treating novel forms of food production, such as algaculture and cellular agriculture, in the same way may help them develop commercially .
The Economist's overview of agricultural intensification options.
National Geographic has profiled the Dutch greenhouse industry.
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