Calcular o carbono em vez das calorias
Um excelente artigo sobre as cálculos de carbono dos alimentos. É preciso quantificar o que não sabemos e estudar toda a cadeia, não chega assumir que é "green" e por isso tem menor impacto.
Mas há tantas variáveis, que uf!
Às vezes dou por mim a demorar uma eternidade de tempo no supermercado. Normalmente sou indecisa, mas com este tipo de informação, perco ainda mais tempo. Vejo a origem dos alimentos, penso no método de produção, nos frescos tento lembrar-me do que será da época...e além disto tudo é preciso saber como cozinhá-los! O que para mim é ainda mais um factor de entusiasmo.
Transcrevo a resposta à uma grande pergunta: peixe selvagem ou de aquacultura?
She describes the resulting carbon calculator as "version 1.0 of a good idea". It doesn't give you the derivation of the figures, but it will tell you that 333 grams of CO2eq is emitted to make one hard-boiled egg. Compare that with a bowl of cereal with milk: 1224 grams of CO2eq - equivalent to driving a typical SUV 6 km.
However, Peter Tyedmers, an ecological economist at Dalhousie University in Nova Scotia, Canada, warns that such calculators should be taken with a pinch of salt. Tyedmers and his students provided much of the raw data for the calculator, and while he agrees it is a good idea in principle, he says the figures they came up with are specific not just to the precise types of foods they measured, but to every detail of where and how they were produced, so cannot be generalised. For example, regional differences in farming practices can make a big impact on the final figure, he says. Simply changing an animal's feed can have a huge impact on its CO2eq footprint too. "It's all very fluid," says Tyedmers. "There's a tremendous hunger for these sorts of numbers and this has created the assumption that any existing figures are robust. They're not."
Farmed vs wild fish
Tuna, cod and other deep-water fish all require fleets of fishing vessels scouring the seas in search of a catch. Since some of these fish can now be grown in fish farms, this would sound like a much less carbon-intensive means of production, since it all but eliminates fuel usage. Can it really produce lower greenhouse gas emissions?
No one has yet done a rigorous comparison of the various aquaculture schemes with industrial fishing, but Stuart Bunting, who specialises in aquatic resource management at the University of Essex in Colchester, UK, says that back-of-the-envelope calculations show where the major carbon emissions lie. One of the most carbon-intensive stages of fish farming is producing fishmeal, he says.
For cage-based costal salmon farming, which relies on currents and tides to remove waste, 90 per cent of the greenhouse gases result from fishmeal production. Further energy is spent rearing the salmon smolts to a size where they can be released in the cages. In contrast, land-based closed containment requires less fishmeal, but instead consumes energy in keeping the fish tanks clean and at the right temperature, and so produces more greenhouse emissions overall.
One way to improve fish farming may be to look to traditional Chinese aquaculture, in which herbivorous and omnivorous species are reared in the same pond. This ecosystem-based approach allows plants to serve as food for animals higher up. This approach eliminates the need for greenhouse-gas-intensive fishmeal. Unfortunately, China's growing appetite for carnivorous fish is leading farmers to adopt western-style aquaculture, feeding the animals fishmeal and fish oil, at the expense of the traditional method's environmental benefits, says Bunting.
Farmed shrimp have a particularly large carbon wake. This industry has destroyed more than 30 per cent of the world's coastal mangroves. Like rainforests, mangroves are carbon sinks. When they are drained and cleared they release both CO2 and methane.
What's more, it takes at least two kilos of fish and squid meal to produce a kilo of shrimp. That means not only a net protein loss, but a hefty carbon trail just to produce these creatures' food. To make things worse, these shrimp are often flown to the west.
If you want to choose fish with a low carbon footprint Bunting and Pelletier recommend farmed herbivorous species - tilapia, carp, bream and catfish.
When it comes to wild seafood, "marine capture fisheries" - fishing fleets in the open ocean - are completely dependent on fossil fuels, as well as being susceptible to overfishing. They account for 1.2 per cent of global oil consumption and emit more than 130 million tonnes of CO2 into the atmosphere per year. That is equivalent to the amount of oil used by the Netherlands, says Tyedmers, which is the 18th largest oil consumer on the planet. However, actual oil usage varies wildly depending on the type of catch. Small fish like herring and anchovy that travel in schools can be captured for 50 litres a tonne, whereas shrimp, tuna, swordfish, sole and flounder can require up to 40 times that.
Mas há tantas variáveis, que uf!
Às vezes dou por mim a demorar uma eternidade de tempo no supermercado. Normalmente sou indecisa, mas com este tipo de informação, perco ainda mais tempo. Vejo a origem dos alimentos, penso no método de produção, nos frescos tento lembrar-me do que será da época...e além disto tudo é preciso saber como cozinhá-los! O que para mim é ainda mais um factor de entusiasmo.
Transcrevo a resposta à uma grande pergunta: peixe selvagem ou de aquacultura?
She describes the resulting carbon calculator as "version 1.0 of a good idea". It doesn't give you the derivation of the figures, but it will tell you that 333 grams of CO2eq is emitted to make one hard-boiled egg. Compare that with a bowl of cereal with milk: 1224 grams of CO2eq - equivalent to driving a typical SUV 6 km.
However, Peter Tyedmers, an ecological economist at Dalhousie University in Nova Scotia, Canada, warns that such calculators should be taken with a pinch of salt. Tyedmers and his students provided much of the raw data for the calculator, and while he agrees it is a good idea in principle, he says the figures they came up with are specific not just to the precise types of foods they measured, but to every detail of where and how they were produced, so cannot be generalised. For example, regional differences in farming practices can make a big impact on the final figure, he says. Simply changing an animal's feed can have a huge impact on its CO2eq footprint too. "It's all very fluid," says Tyedmers. "There's a tremendous hunger for these sorts of numbers and this has created the assumption that any existing figures are robust. They're not."
Farmed vs wild fish
Tuna, cod and other deep-water fish all require fleets of fishing vessels scouring the seas in search of a catch. Since some of these fish can now be grown in fish farms, this would sound like a much less carbon-intensive means of production, since it all but eliminates fuel usage. Can it really produce lower greenhouse gas emissions?
No one has yet done a rigorous comparison of the various aquaculture schemes with industrial fishing, but Stuart Bunting, who specialises in aquatic resource management at the University of Essex in Colchester, UK, says that back-of-the-envelope calculations show where the major carbon emissions lie. One of the most carbon-intensive stages of fish farming is producing fishmeal, he says.
For cage-based costal salmon farming, which relies on currents and tides to remove waste, 90 per cent of the greenhouse gases result from fishmeal production. Further energy is spent rearing the salmon smolts to a size where they can be released in the cages. In contrast, land-based closed containment requires less fishmeal, but instead consumes energy in keeping the fish tanks clean and at the right temperature, and so produces more greenhouse emissions overall.
One way to improve fish farming may be to look to traditional Chinese aquaculture, in which herbivorous and omnivorous species are reared in the same pond. This ecosystem-based approach allows plants to serve as food for animals higher up. This approach eliminates the need for greenhouse-gas-intensive fishmeal. Unfortunately, China's growing appetite for carnivorous fish is leading farmers to adopt western-style aquaculture, feeding the animals fishmeal and fish oil, at the expense of the traditional method's environmental benefits, says Bunting.
Farmed shrimp have a particularly large carbon wake. This industry has destroyed more than 30 per cent of the world's coastal mangroves. Like rainforests, mangroves are carbon sinks. When they are drained and cleared they release both CO2 and methane.
What's more, it takes at least two kilos of fish and squid meal to produce a kilo of shrimp. That means not only a net protein loss, but a hefty carbon trail just to produce these creatures' food. To make things worse, these shrimp are often flown to the west.
If you want to choose fish with a low carbon footprint Bunting and Pelletier recommend farmed herbivorous species - tilapia, carp, bream and catfish.
When it comes to wild seafood, "marine capture fisheries" - fishing fleets in the open ocean - are completely dependent on fossil fuels, as well as being susceptible to overfishing. They account for 1.2 per cent of global oil consumption and emit more than 130 million tonnes of CO2 into the atmosphere per year. That is equivalent to the amount of oil used by the Netherlands, says Tyedmers, which is the 18th largest oil consumer on the planet. However, actual oil usage varies wildly depending on the type of catch. Small fish like herring and anchovy that travel in schools can be captured for 50 litres a tonne, whereas shrimp, tuna, swordfish, sole and flounder can require up to 40 times that.