Re: the power of junk, Is Parallel Programming Hard, And, If So, What Can You Do About It?

BGB wrote:

On 5/24/2025 4:45 PM, Michael S wrote:

On Sat, 24 May 2025 20:36:50 -0000 (UTC)
John Levine <johnl@taugh.com> wrote:
>

According to BGB  <cr88192@gmail.com>:

Don't forget to factor in energy costs.  The energy costs
to refine and produce virgin aluminum are very high, relative
to the costs of recycling aluminum.

>
Granted, but possibly depends on the relative cost of energy.
>
But, likely, as more total aluminum is produced the relative cost of
aluminum would go gown. While recycling aluminum makes sense, it
does come with the tradeoff that recycling aluminum reduces the
relative cost of aluminum (and thus the value of producing new
aluminum would go down), so is less likely to be favored by the
primary producers (where a relative scarcity is better for profit
margins, ...).

>
Aluminum is produced from bauxite which is around 40% aluminum and
needs a multi-step energy intensive process to turn into metallic
aluminum.  But aluminum scrap is already metallic aluminum.  My
impression is that we are about as far down the experience curve as
we are likely to get, and using scrap as a source will always be far
cheaper than bauxite.
>

>
Aluminum from bauxite is almost pure aluminum. Aluminum from scrap
contains significant and unpredictable amounts of magnesium, copper and
silicon. Removing them is hard, in case of copper very hard.
>

 Possibly why aluminum cans are "more favorable" for recycling, as the alloy the cans are made of is pretty much pure aluminum.

The can itself (bottom plus cylinder side) is quite pure Al, but the lid is an alloy with enough Mg added to make an impact on worldwide magnesium consumption.
For remelting you would preferably have a way to separate the lids from the rest of the cans.
Terje
--
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"