In recent years, synthetic or cultured meat has been presented as “the greatest hope for veganism.” This is meat grown artificially in the laboratory, so we can continue to consume meat without the need for large-scale breeding of animals for the purpose of slaughter.The arguments for cultured meat are not limited to animal welfare, since meat grown in a laboratory can also help reduce environmental damage caused by animal husbandry. According to estimates by the Food and Agriculture Organization (FAO) of the United Nations, agricultural livestock, especially cattle, account for about 14.5% of the world's greenhouse gas emissions, and thus contribute to climate change.Forty-four percent of these emissions are methane (CH4) and 29% are nitrous oxide (N2O); both cause a greater greenhouse effect than carbon dioxide.Emissions are not the only environmental cost for the meat industry: about 30% of the world's land, not including that covered by ice, is used to grow livestock ; forests are cleared to prepare land for grazing or to make room for crops to be used for animal feed; about 8% of fresh water is directly or indirectly used for raising animals.In an article from 2012, researchers Mesfin Mekonnen and Arjen Hoekstra from the University of Twente in the Netherlands estimate that more than 15,000 liters of water are needed to produce one kilogram of beef. In addition, the meat industry pollutes water sources and consumes large amounts of energy, mainly in the form of fossil fuels.Despite this, demand for meat worldwide is growing, partly due to the continued growth of the world's population with the improvement of living conditions in developing countries such as India and China. The FAO predicts that by 2050 meat consumption will grow by more than 70% compared to its 2010 level.According to those who advocate the development of cultured meat, the move to synthetic meat will help preserve the planet. In support of this, the advocates cite the results of a theoretical study from 2011 according to which, under ideal conditions, cultured meat would use 99% less land, emit 96% less greenhouse gas, consume 96% less water and demand 45% less energy than beef produced today. The difficulty is to make these ideas practical.On April 5, 2013, the first hamburger prepared from beef grown in the laboratory was presented to the public. This caused a media tsunami with hundreds of journalists covering the live taste test.The tasters seemed less enthusiastic. One of them described the taste of the hamburger as “close to meat,” yet none of the tasters was quick to take another bite. The cost of this hamburger was also quite high: about $325,000 for a 140-gram ration, funded mostly by Google co-founder Sergey Brin.However, considering that this hamburger was made only to prove feasibility, this was a “good start,” said the proud inventor of the artificial meat, Prof. Mark Post from the University of Maastricht in the Netherlands.For the making of this meat patty, Post took a sample from the shoulder muscle of a cow in a slaughterhouse. From this he produced satellite cells, which are found in skeletal muscles and can repair damaged muscle tissue. Post grew them in a rich liquid medium, which included hormones and nutrients and was partly composed of fetal bovine serum.The cells multiplied until Post transferred them to small plastic plates containing collagen – an animal protein that serves as a kind of scaffold for growing cells – and a nutrient-poor medium. In response to this starvation, the satellite cells became muscle cells, lining up on the scaffold and merging with one another to form small rings of extremely thin muscle fibers.Like our muscles, muscle fibers grown in laboratory dishes need exercise to keep them from deteriorating and to ensure they continue growing and developing. Post attached the small muscle rings to plates to induce the same tension that muscles experience in training – kind of a miniature gym.After the muscle rings expanded, Post cut them into thin strips, using about 20,000 strips to prepare the hamburgers he served to the taste testers. The whole process took about three months – less than a third of the time needed to grow a cow for human consumption.POST’S HAMBURGER was grayish and did not resemble the meat we are familiar with, which is reddened by the protein myoglobin. This protein contains an iron ion and binds oxygen, similar to hemoglobin in the blood, so rich red meat is therefore rich in iron.Since Post's cultured meat does not have a blood system that will carry oxygen and nutrients deep into the tissue, it has been grown as thin strips in a very oxygen-rich environment. An undesirable side effect of this was a reduction in the expression of myoglobin in muscle cells, and therefore in iron content and red color.To give the artificial flesh a red tinge, Post added saffron and beet juice to the patty, as well as crumbs of bread and salt. Also, unlike real meat, the meat of this experiment contained only muscle cells – no fat cells – and so it was fried in generous quantities of butter.To succeed in creating artificial flesh to replace what nature has given us, we will have to closely mimic the composition and texture of animal meat at a reasonable cost. The meat Post presented in 2013 was very expensive, but he estimates that the cost of a similar steak today would be just over $11. In addition, he is currently developing artificial meat that will contain both muscle cells and laboratory-grown fat cells, so the next version of his hamburger will be even closer to the meat we know.But is it possible to grow a large and juicy steak that resembles the real thing and is made up of muscle cells, fat, blood vessels, and connective tissue, just like animal tissue? Artificially growing such pieces of meat is not a new idea. As early as 1931, Winston Churchill wrote, “Fifty years hence… we shall escape the absurdity of growing a whole chicken in order to eat the breast or wing, by growing these parts separately under a suitable medium.”Churchill misjudged the time it would take, but researchers and companies around the world are now trying to make his vision a reality. In Israel, the Modern Agriculture Foundation, founded in 2014, and comprised mainly of vegetarians and vegans, promotes research aimed at creating cultured poultry. Chicken was decided on, because of its popularity both in Israel and in many other countries.In January 2015, the organization initiated a feasibility study under the direction of Prof. Amit Geffen of the Department of Biomedical Engineering at Tel Aviv University. The aim of the study was to examine the obstacles and solutions to making a chicken breast. The tests were expected to end at the beginning of the year, but when asked about the project, Geffen replied that he was no longer involved.However, in July 2016, a mass funding campaign was launched for an Israeli entrepreneurial venture consisting of eight people, called SuperMeat. The company was founded in December 2015 and includes quite a few members from the Modern Agriculture Foundation. The goal of the company is to create “real” chicken meat without killing chickens, based on the research of Prof. Yaakov Nahmias, head of bioengineering at the Hebrew University of Jerusalem and one of the founders of Super-Meat.One of the main limitations to growing a thick slice of meat in the laboratory is the difficulty of supplying oxygen and nutrients deep within the growing tissue. Without this, the thickness of the tissue cannot exceed 0.3 millimeters, like that of Post’s meat strips. In the living body, oxygen and nutrients reach all regions of the tissue through blood vessels, and in 2006 Nahmias showed this system can be imitated when he cultured liver tissue in a human body with a blood-like system. He plans to use a similar method to grow larger pieces of chicken, in order to get muscle tissue similar to the size of chest muscle.Another problem is the use of animal products. Post raised his meat cells on a bed of serum produced from cow fetuses, a breeding method that does not exempt us from dependence on animals and is not without its own moral problems.Most animal cells grown in the lab require serum, but in Nahmias’s laboratory they didn’t use it to grow liver cells, instead using an alternative, serum-free growth medium. Nahmias and his colleagues even published a paper a year ago in which they showed genetically modified human liver cells can be grown using this alternative and result in a huge number of cells – 10,000 trillion – which, according to Nahmias, would weigh about 80 tons.To grow properly, cultured cells need a few more animal-derived substances, but they can be easily replaced with materials derived from, for example, genetically engineered plants. Even Post has gone on to grow his cultivated meat on a serum-free medium. In order to grow the chicken, Nahmias and his colleagues at SuperMeat intend to take small samples of tissue from different chickens (to preserve genetic diversity) and isolate mesenchymal cells. According to Nahmias, these cells do not need serum to grow and can differentiate into both muscle and fat cells. And unlike the satellite cells used by Post, which need to be replenished from time to time, Nahmias's cells are everlasting and can be a constant source of new cells. In other words, after successfully isolating samples from a chicken, which can be released unharmed, no additional samples are needed. In fact, if SuperMeat successfully grows artificial chicken pieces, chickens will no longer be needed for meat.According to SuperMeat's vision, some of the cells produced from the chickens will be grown in a special machine called a bioreactor, which mimics some of the natural conditions required for the development of muscle tissue in live poultry, such as exposure to certain hormones.Under these conditions, the cells get organized into small muscle tissue at a length of a few millimeters, which would be packed in capsules and sent to the company's customers. The customers would put the capsules in a machine that the company would develop, where growth powder and water will be added, and the small muscle tissue will continue to develop into a large chicken sections.Nahmias predicts that the process of growing a kilogram of chicken meat in such a machine would take around 20 days and cost no more than five dollars.Cultured meat, of course, may have different nutritional values than regular meat, as was the case for Post’s low-iron meat. In this case, artificial vitamins, minerals and other substances will need to be added. Also, as a new food product it will have to be regulated to ensure its quality and safety for human consumption.For observant Jews there may be another problem that would require the attention of a supervising body: is cultured meat kosher? At the moment, the opinions are divided, with some rabbis who claim that it is not considered meat at all, and therefore even cultured pork would be kosher.But there are also rabbis who think it is meat in all respects, so it would require some sort of rabbinical supervision. It is interesting to consider how “kosher slaughter” would be defined under these conditions.It is very likely that the cheap production of artificial meat that is as similar as possible to real meat will reduce the number of animals slaughtered for food, but meat is not the only animal product used by humans: eggs and milk are very popular food products (although there is also artificial milk created by genetically engineered yeast), and there are many other animal products used in various industries – feathers, blood, skin, internal organs and more.These contribute a significant percentage of the current pollution. In fact, in general, cultured meat is friendlier from the environmental aspect only if you examine cattle growing. If you compare cultured meat to naturally grown chickens and pigs, which are also very popular, you would find that is not the case.THERE ARE also studies that claim that cultured meat is not necessarily preferable from the environmental perspective. In contrast to the 2011 study, which examined the environmental impact of cultured meat grown in ideal conditions, studies that examined more realistic conditions showed that, in many cases, animal husbandry is less polluting to the environment than cultured meat.A 2015 study demonstrated that cultured meat would use less land than the current meat industry, similar to what the previous study showed. However, its energy consumption is greater than that required for raising pork, chicken and even beef.Also, the production of cultured meat emits more greenhouse gases than the production of pork and chicken in the meat industry today. According to the study, it seems that cultured meat would be environmentally friendlier than beef, but not for chicken or pork (not to mention insect meat).If SuperMeat succeeds in translating Nahmias's success in growing human liver tissue into growing cultured chickens, they will probably not reduce the environmental damage caused by growing animals. However, once they have managed to grow a piece of chicken, it would theoretically be possible to apply their technology to the meat of any other animal.In any case, even if cultured meat does not save the environment, it will at least allow those interested in eating a piece of meat to know that it came from an animal that is still living and free. The writer has a PhD in life sciences from the Weizmann Institute of Science, and is a writer at the Davidson Institute of Science Education.