<story><title>Harnessing heat from wastewater</title><url>https://www.bbc.co.uk/future/article/20240103-sewage-a-low-cost-low-carbon-way-to-warm-homes</url></story><parent_chain><item><author>ak217</author><text>I&amp;#x27;m amazed at how little district heating is used in northern climates like Canada and the northern US. In dense areas, district heating using waste heat from power plants should really be required by urban planners, or at least it would make a huge carbon footprint difference if we invest in it.&lt;p&gt;On an individual household scale, I&amp;#x27;ve always wondered why nobody has come up with basic drain heat exchangers to capture most of the heat coming out of shower and washing machine wastewater before it leaves the building. (Edit: I guess they do exist - &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.homedepot.com&amp;#x2F;p&amp;#x2F;Power-Pipe-4-in-x-48-in-Drain-Water-Heat-Recovery-Unit-R4-48&amp;#x2F;203456049&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.homedepot.com&amp;#x2F;p&amp;#x2F;Power-Pipe-4-in-x-48-in-Drain-Wa...&lt;/a&gt; - but I&amp;#x27;ve never seen one in the wild)</text></item></parent_chain><comment><author>miketery</author><text>It&amp;#x27;s a cost thing. Prices for energy have been so cheap that investing in recapture capex didn&amp;#x27;t make sense. With energy prices going up, it does make sense.&lt;p&gt;A funny anecdote (or sad?), after gas prices spiked in much of Europe due to the war many manufacturing facilities were looking to cut energy use, they found a lot of waste. Many places were able to reduce their gas usage by as much as ~33% if I recall correctly.&lt;p&gt;I can&amp;#x27;t find the original source, but here&amp;#x27;s [1] one that claims 23% lower consumption across Germany in 2022 adjusted for temperature.&lt;p&gt;1 - &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.nature.com&amp;#x2F;articles&amp;#x2F;s41560-023-01260-5&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.nature.com&amp;#x2F;articles&amp;#x2F;s41560-023-01260-5&lt;/a&gt;</text></comment>
<story><title>Harnessing heat from wastewater</title><url>https://www.bbc.co.uk/future/article/20240103-sewage-a-low-cost-low-carbon-way-to-warm-homes</url></story><parent_chain><item><author>ak217</author><text>I&amp;#x27;m amazed at how little district heating is used in northern climates like Canada and the northern US. In dense areas, district heating using waste heat from power plants should really be required by urban planners, or at least it would make a huge carbon footprint difference if we invest in it.&lt;p&gt;On an individual household scale, I&amp;#x27;ve always wondered why nobody has come up with basic drain heat exchangers to capture most of the heat coming out of shower and washing machine wastewater before it leaves the building. (Edit: I guess they do exist - &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.homedepot.com&amp;#x2F;p&amp;#x2F;Power-Pipe-4-in-x-48-in-Drain-Water-Heat-Recovery-Unit-R4-48&amp;#x2F;203456049&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.homedepot.com&amp;#x2F;p&amp;#x2F;Power-Pipe-4-in-x-48-in-Drain-Wa...&lt;/a&gt; - but I&amp;#x27;ve never seen one in the wild)</text></item></parent_chain><comment><author>quickthrowman</author><text>&amp;gt; In dense areas, district heating using waste heat from power plants should really be required by urban planners&lt;p&gt;Power plants generally aren’t located in dense areas…&lt;p&gt;&amp;gt; I&amp;#x27;m amazed at how little district heating is used in northern climates like Canada and the northern US.&lt;p&gt;District heating and cooling are available in both Mpls and St Paul in the downtown core. This is the coldest large metro area in the United States.&lt;p&gt;St. Paul: &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.districtenergy.com&amp;#x2F;&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.districtenergy.com&amp;#x2F;&lt;/a&gt;&lt;p&gt;Minneapolis: &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;cordiaenergy.com&amp;#x2F;our-networks&amp;#x2F;minneapolis&amp;#x2F;&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;cordiaenergy.com&amp;#x2F;our-networks&amp;#x2F;minneapolis&amp;#x2F;&lt;/a&gt;&lt;p&gt;&amp;gt; On an individual household scale, I&amp;#x27;ve always wondered why nobody has come up with basic drain heat exchangers to capture most of the heat coming out of shower and washing machine wastewater before it leaves the building. (Edit: I guess they do exist - &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.homedepot.com&amp;#x2F;p&amp;#x2F;Power-Pipe-4-in-x-48-in-Drain-Wa&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.homedepot.com&amp;#x2F;p&amp;#x2F;Power-Pipe-4-in-x-48-in-Drain-Wa&lt;/a&gt;... - but I&amp;#x27;ve never seen one in the wild)&lt;p&gt;$851 just for the heat exchanger, not including piping and labor. It will take a lot of showers and laundry to pay that back. I’d probably add one to a new house build but would pass on retrofitting one into an existing home unless I was doing a complete plumbing remodel. Similar to daylight harvesting LED lighting, it’s possible you’ll never see a payback on the equipment and labor.</text></comment>