The farmers at La Paz's coca market greet each other with affection. They only get to meet like this once every three months, when their crop of coca leaves is harvested.
Chewing coca leaves is a way of life for many Bolivians
Twenty thousand farming families from Bolivia's central Yungas region depend on this market. Few foreigners come here, and when they do they are greeted with suspicion.
"It's not a drug," shouts one youth as he loads sacks of coca onto a truck. "It's good for you."
Inside the market traders unfasten coloured sacks filled with coca, grasping handfuls of leaves for examination. Coca is selling at just over $4 (£2) per kg (2.2lb).
Eucevio Alejo is a coca farmer and manager of the market.
"The coca leaf is life," he says as he passes people queuing to exchange their coca for grains and potatoes.
"It allows me to feed my five children and send them to school. It is the only economic means I have."
Traders need to have a licence to buy or sell coca at the market, and anyone found to be involved in the narcotics trade is cast out - not just from the market, but from their community too.
The coca here is intended for traditional use only.
Coca leaves are used in medicine and cooking. Mostly they are made into tea and chewed, alleviating altitude sickness, fatigue and hunger.
Inside the market, there is the distinctive grass-like smell of coca. Outside, there is the familiar debris of dark green clumps, chewed up and spat out.
But for Bolivia's Aymara and Quechua Indians coca is more than just sustenance.
"Everything has its physical form, personality and spirit for indigenous communities. The way we relate to everything around us is through coca," says Sdenka Silva, co-founder of La Paz's Coca Museum.
"With coca there is no cheating or lying because it is sacred. With coca you are never alone, because you are always connected to the Pachamama, or Mother Earth."
Coca export plans
But traditional Andean culture is not what governs the majority of coca cultivation.
According to UN figures for 2005-2006, just over 14 million worldwide people use cocaine. More than six million of these are in North America, while the UK, Spain and Italy have the highest rates of cocaine consumption in Europe.
Bolivia is the third-largest coca producer in the world.
In the past, anti-cocaine policies have also often meant anti-coca policies, but that changed when a former coca farmer, Evo Morales, came to power in December 2005.
Mr Morales wants to industrialise coca, a move he says will benefit Bolivia and help in the fight against drugs.
Prudencio Ticona would like to be able to export his goods
The president has appointed a coca minister, wants coca included in Bolivia's new constitution and has approved the construction of three coca-processing plants.
"Through industrialisation we can regulate and control coca," says Sabino Mendoza, a member of the Constituent Assembly, which is drafting the constitution.
"Industrialisation is a priority, but not just in Bolivia. We want to export coca throughout the world."
Currently, Ingacoca is the only legally-certified company producing coca products in Bolivia.
"On these shelves we have syrups and creams," says Prudencio Ticona, one of four brothers who run the company.
"We have products for diabetes, slimming, muscular pains; this one is good for nerves," he says, proudly pointing at a row of bottles.
Mr Ticona says there is international interest, especially from Russia, in importing his products.
But under international law he cannot export unless he proves the coca has been used as a flavouring agent and that alkaloids, which are made into cocaine, have been removed.
UN conventions list coca as a dangerous controlled substance, along with cocaine and opium. Evo Morales has been lobbying for it to be taken off the list when the UN Commission on Narcotic Drugs meets in 2009.
His government says more countries would import natural coca if it were not outlawed.
Last year he told the UN General Assembly: "The green coca leaf is not the white of cocaine, this coca leaf represents Andean culture. It is a coca leaf that represents the environment and the hopes of our people".
But Bolivia faces major opposition in its campaign, not least from the United States, which is against efforts to industrialise and export coca and any proposals to change international law concerning coca.
Eucevio Alejo cannot understand opposition to selling coca
At a recent news conference, the US ambassador to Bolivia, Philip Goldberg, told journalists that it was worrying that in the country more cocaine was being cultivated, more cocaine produced and more consumed.
As the day draws to an end, Eucevio Alejo prepares to leave the coca market. He is baffled by foreign attitudes to coca, a plant that means so much to him.
The amount paid for 1g of cocaine in the UK would feed Eucevio's family for a fortnight. But it is the cost of the international drugs trade for Bolivia that concerns him.
"I do not know who they are, the people who use coca to make drugs or the people who use cocaine, " he says.
"'But what they are doing is very bad. It goes against us. It hurts small coca farmers, and it punishes Bolivia."