The following categories exist on the wiki, and may or may not be unused. Also see wanted categories.
- Rio de Janeiro (5 members)
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- Rural community development (75 members)
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- SCRAP Humboldt (7 members)
- SDG01 No poverty (9 members)
- SDG02 Zero hunger (250 members)
- SDG03 Good health and well-being (1,297 members)
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- SDG06 Clean water and sanitation (432 members)
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- SDG08 Decent work and economic growth (220 members)
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- SDG10 Reduced inequalities (219 members)
- SDG11 Sustainable cities and communities (1,052 members)
- SDG12 Responsible consumption and production (505 members)
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- SDG14 Life below water (44 members)
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- Thailand (13 members)
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- TheFWD (6 members)
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- The Gambia (1 member)
- The Green Web Foundation (22 members)
- The Hyphae Journal (7 members)
- The Open Toolbox (4 members)
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- Therapy (7 members)
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- Theses (1 member)
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- Three Acres and Liberty (30 members)
- Tibial Fracture Fixation (47 members)
- Tidal power (6 members)
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- To Catch the Sun (9 members)
- Tobacco (5 members)
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- Tolocar (72 members)
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- Tool construction manuals (5 members)
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- Topics (541 members)
- Towards sustainable economies (11 members)
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- Tracking categories (63 members)
- Traditional Cheesemaking (7 members)
- Traditional Field Crops (11 members)
- Tran sport (1 member)
- Transition Towns (4 members)
- Transparency (2 members)
- Transport (178 members)
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- Transportation (8 members)
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- Trees (45 members)
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- Trillium Charter School (8 members)
- Trinity County, California (1 member)
- Tropical plants (2 members)
- Tuberculosis (1 member)
- Turbine (1 member)
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- USA (532 members)
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- Uganda (9 members)
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- Ultrasonic Sensors (2 members)
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- Upcycling (142 members)
- Urban agriculture (90 members)
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- Urban sustainability (8 members)
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- Urban sustainability by location (1 member)
- User:Verkssuwey/Blog (0 members)
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- Utensiles (1 member)
- V-Y Advancement Flap (6 members)
- VITA (9 members)
- VOC (1 member)
- VTA Skillset (9 members)
- Vaccination (1 member)
- Vaccine refrigeration (7 members)
- Vancouver (1 member)
- Vegetable oil fuel (29 members)
- Vegetable oils (36 members)
- Vegetables (54 members)
- Vegetarianism and veganism (16 members)
- Vehicle modification (3 members)
- Vehicles (1 member)
- Vermiculture (28 members)
- Vertical gardens (2 members)
- Victoria (Australia) (9 members)
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- Wind power (54 members)
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- Young and beginning farmers (2 members)
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- Zef upcycling (6 members)
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- 한국어 (2 members)