Who We Are
Herr Ltd is an ecological water and wastewater design company based in Dundalk, County Louth. We’ve been designing and supplying low-energy water systems for Irish homes since 1992 — over three decades of practical, plant-based solutions that work with nature rather than against it.
We work with self-builders, architects, and rural homeowners across Ireland to design systems that reduce mains water use, treat wastewater naturally, and recover nutrients that would otherwise pollute rivers and groundwater.
Meet Ollan Herr
Herr Ltd is run by Ollan Herr, a water systems designer and engineer with more than 30 years of experience in ecological wastewater treatment.
Ollan’s work goes beyond standard treatment. He has spent years developing systems that extract phosphorus and nitrogen from separated urine — nutrients that are both a major source of river pollution and a finite, increasingly costly resource for global food production. His approach turns what is usually a waste disposal problem into a resource recovery opportunity.
He is a recognised voice in Ireland on sustainable water management, and has been advocating to government for urine separation and phosphorus recycling as part of a long-term national water strategy.
“Ollan Herr is without doubt one of the most important people working in sustainable construction in this country.” — Brian T O’Brien, Solearth Architecture (client since 2010)
“Ollan is one of the very few genuinely environmentally friendly wastewater treatment consultants in Ireland. Ask him a question and you’ll very quickly know everything you need to about nitrates, phosphates, reed beds, wetlands, and hydroponics.” — Jan Vreenegoor, Director, AMMANU (client)
Our Approach
We design systems that use as little energy as possible — ideally none at all. Most of our systems rely on gravity, plants, soil, and biology rather than pumps, electricity, or chemicals.
Our work covers:
- Composting and waterless toilets — modern, odour-free systems that separate and compost toilet solids using earthworms
- Urine treatment and nutrient recovery — removing phosphorus and other pollutants from separated urine so they can be safely reused as fertiliser
- Reed bed sewage treatment — using reeds, willows, and flowers to naturally treat domestic wastewater
- Rainwater harvesting — gravity-fed collection systems for toilet flushing and household use
- Greywater recycling — treating and reusing water from showers and sinks
We also work alongside architects from the early stages of design, producing drawings, specifications, and compliance documentation for EPA Code of Practice requirements.
Why It Matters
The world’s reserves of phosphate rock — the source of most mineral fertiliser — are finite and already becoming costly. At the same time, human and animal urine is the primary source of phosphorus and nitrogen polluting Ireland’s rivers and waterways.
Herr systems close that loop. The phosphorus we recover is free of pharmaceuticals and heavy metals, making it safe to use as fertiliser in the human food chain. The flower-growing systems we design for nitrogen removal are not just functional — they’re genuinely beautiful.
We believe ecological sanitation is not a compromise. Done well, it produces cleaner water, healthier gardens, and a more resilient food system.
Other Projects
Rotovelo — Available in Ireland through Herr Ltd
Ollan is also the Irish supplier for the Rotovelo, a super-lightweight velomobile designed for all-weather commuting. Fast, pedal-powered, and fully rain-proof, it’s a natural fit for anyone interested in low-energy, ecological living.
Find out more at velocycle.ie.
Get in Touch
If you’re planning a new build, upgrading an existing system, or working on a project that needs ecological water and wastewater expertise, we’d love to hear from you.
Tel: +353 (0)42 9377689
Mob: +353 (0)86 1700569
Or send us a message