Even with fully-developed technology, I have a hard time believing it will require less energy to manufacture a pound of synthetic beef than it will to simply grow it naturally. Am I wrong?
But there are huge costs (monetary and energy) in scaling "breed, fatten & slaughter a lot of cows", and in intensive operations, they're largely fed on pre-prepared feed from corn or whatever.
Things like feedlot construction/maintenance, feed delivery, waste disposal, transport to slaughter/butchering all contribute above the feed costs.
I'm not sure how the artificial alternative would stack up, but most of those other factors can be eliminated or reduced, and (depending on feedstocks to the clone growing) bypassing the energy costs of growing, harvesting and processing of the vegetable feed.
From the very narrow perspective of energy efficient, the problem I see is that we are ditching a true and tested method of doing things with (up to a point) renewable resources and trying to create a substitute most likely based on petrochemicals, just at the same time as we're dragging our feet on finding and deploying a viable alternative to petrol based energy systems.
Historically speaking, one of the reasons[1] domestication of large herbivores for meat production makes sense is because those can be fed with agriculture byproducts not suitable for human consumption. In industrial terms, it is a sort of "rejects reprocessing" that partially recovers an investment that was already lost.
Nowadays, we feed our animals with human suitable food, which is possible due to the (cost) efficiency gains of the green revolution, which originally was mostly about petrochemicals.
[1] the other being that in nomad societies, they constitute a food store that can carry its own weight around.
And using the same kind of biotech we use to break down cellulose to make cellulosic ethanol, we might be able to create feedstock for this meat from agricultural waste or fast-growing grasses.
* Starches from corn or potatoes is pretty cheap (money, heavily affected by federal subsidies).
* Synthetic meat can use it more efficiently (the engineer in me wants to say "energy", but depending on the context it may mean higher utility margins, or lower labor costs, or what not).
* Same kind of biotech [as] cellulosic ethanol. I am not familiar with the state of the art on this field, but (corn) ethanol companies just engages in arbitrage tricks to make a bundle on yuppie's eco-guilt and government's largesse. Both the economy and the environment would be better of if people just shut up and directly burnt the diesel used in machinery used to rise and transport the corn used as raw inputs to make the ethanol.
Not that this particular argument is wrong, just that I do not have the facts and would like to see them discussed without all the hype!