Nutrient loading in coastal ponds has inevitably led town planners all across the Cape and Islands to the prospect of increased sewering. At a presentation on the Vineyard this week, Earle Barnhardt and Hilde Maingay of the Citizens for Economic and Ecological Sustainability of Falmouth offered a different vision. Rather than a centralized municipal solution, they offered a modular, personalized one.

In short, they were spreading the good news of composting toilets.

“There are resources that are built into our human waste that are resources that we should be using,” Ms. Maingay said bluntly.

With down-Island towns prepared to undertake major sewering projects, some 40 concerned residents came to the presentation at Howes House in West Tisbury on Wednesday night to learn how not to waste their waste.

All the most commonly proposed solutions for stemming the flow of harmful nitrogen into coastal ponds are deficient, Mr. Barnhardt and Ms. Maingay said. Shellfish propagation alone isn’t up to the task. Permeable reactive barriers — a trench along the beach filled with woodchips and denitrifying microorganisms of the kind undertaken at two ponds in Falmouth, they argue, is not scaleable. Meanwhile sewers, which Mr. Barnhardt and Ms. Maingay see as energy intensive, expensive and dirty, are a nonstarter. Mr. Barnhardt said that his town, Falmouth, was prepared to spend half a billion dollars on sewering projects along the shores of town ponds that have turned sickly green and lifeless from decades of septic system input.

“The cost of the sewer is an almost insurmountable problem, but there are also ecological problems,” Mr. Bernhardt said. Sewer sludge, he said, must be incinerated, releasing heavy metals into the sky while the toxic ash left over must be buried. Perhaps most problematic to Mr. Barnhardt is the wasted potential of nitrogen present in human waste, which must otherwise be synthesized from fossil fuels to make commercial plant fertilizer.

Enter the unsung, and sometimes strange world of composting toilets. Composters, like the darling of Whole Earth Catalog subscribers, the Clivus Multrum, use no water, cutting down a home’s yearly use 30 to 40 per cent. They can also divert up to 88 per cent of a house’s yearly nitrogen output and larger models can store up to two years worth of waste. Over time the waste decomposes (90 per cent of the volume exits a vent as gas) and disinfects, leaving each household a bushel per year of what is unfortunately known as “humanure.”

Mr. Barnhardt readily admitted that some of the earlier models of composting toilets did little to inspire widespread acceptance.

“If we want to propose this on a big scale, these need to be foolproof,” he said after describing in excruciating detail the particular malfunctions of prototypes that more recent models, costing anywhere from $4,800 to $6,300, had largely eliminated. Island Cohousing has operated 17 Clivus models for years without incident.

Other models showcased were urine diverting toilets — essentially a toilet with two targets. Urine accounts for 80 per cent of a household’s annual nitrogen output, and by collecting it and treating it with magnesium oxide crystals (Mr. Barnhardt was hazy on the carbon footprint of magnesium extraction) it can be converted to fertilizer.

But there still remained the problem of what to do with all that fertilizer that had been diverted from groundwater but nonetheless could end up in local water bodies. Some systems include a pick-up service to simply whisk the compost away for use elsewhere, but Mr. Barnhardt had a more novel solution: Grow bamboo. He said an acre of the fast-growing timber can be harvested on the urine of 75 adults. Mr. Barnhardt and Ms. Maingay envisioned an offshoot local economy based on the processing of bamboo for mulch and building material.

“It becomes a job-producing, permanent, nutrient-recovery business,” he said. “We think that that is a lot better for a community to have than to pay for a sewer where all the money goes to the sewer designers, sewer builders and pipelayers and it’s gone.”

Other more outré nitrogen-management suggestions from Mr. Barnhardt included planting invasive water hyacinths in coastal ponds, which he admitted was possibly illegal, and collecting rainwater to drink, effectively disconnecting from the municipal water grid altogether.

Mr. Barnhardt admitted that he faced an uphill political battle in selling his vision.

“Town officials tend to want to go right ahead and sewer,” he said. “They’re less optimistic about this because I think it is administratively simpler for a town administration to collect taxes, hire a firm, build a sewer, collect fees and pay for the sewer. To do what we’re proposing is very complicated.”

“When it comes to these systems they don’t trust people to have any common sense,” added Ms. Maingay.

They also face the obstacle of consumer unfamiliarity with the systems, which have improved dramatically in recent years and require significantly less maintenance and care than in years past. To bridge this gap Ms. Maingay has been contacting towns to have them installed in libraries and town halls.

“We hope that we can find a place where we can have it more publicly accessible,” she said. “We’ve had a lot of people go through our house to use ours but that’s not practical.”

Luckily for Ms. Maingay and her curious houseguests, composting toilets boast another advantage: They are odor-free.