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Hi,
I need your help again.
Can you explain what the bold phrases mean?

Biofuels for aviation have a number of benefits, the most important of which is the reduction in greenhouse gases emitted by aviation – an important conduit of world trade and economic development.
(Are the gases, according to this sentence, a conduit of world trade and economic development? What does conduit mean in here?)

Climate policy costs for airlines may not have more than a marginal impact on the economics of aviation biofuels. From an aviation economics perspective, a more effective approach is to use positive economic measures at an early stage in the development of an aviation biofuel industry than waiting to rely on increasing costs of using fuels, which may come too late for aviation to be a user of biofuels.
(Does the first sentence of this paragraph mean climate policy costs for airlines may have a little impact on the economcis of aviation biofuels? The author seems to say that if we don't use positive economic measures at an early stage in the development of an aviation biofuel industry, that will bring about bad effects. Why does failing to do so cause people to wait to rely on increasing costs of using fuels? )

Thank you.
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1-- No, aviation is an important conduit.
2-- No, 'more than a marginal impact' = a significant impact.
3-- Failing to develop biofuels now is more effective than waiting until high fossil fuel costs force airlines to develop biofuels later.
Comments  
Thank you.

2. 'more than a marginal impact' = a significant impact.
So they may not have a significant impact. Does this mean they may have a little impact? Or they may have little impact?

3. It is still beyond my understanding.
Can I paraphrase the author's meaning like this?
We should use positive economic measures right now, at the early stage of the biofuel industry; we should not wait; if we wait, the fossil fuel price will soar; and when the fossil fuel price soars, it is too late for us to use the biofuel.

Thank you again.