yeah, you could plant grass i guess. but to the topic, i'm not sure i understand? do you mean fiber like plant fiber? or something more like flax seed meal? i use a little of that when i bake bread (IRL). also shelled hemp seeds are delicious.

Flaxseed Meal
Flaxseed Meal is freshly milled to preserve the natural oils and nutrients. Ground flaxseeds have a nutty taste and are a noted health-giving digestive aid. They are also high in fiber and are powerful natural cholesterol controllers. In a 2 Tablespoon serving size (13 grams) the fiber content is 1.33 grams of Soluble Fiber and 2.67 grams of Insoluble Fiber. Ground Flaxseeds are a good source of Omega 3 Fatty Acids. In a 2 Tablespoon serving, there is 2400 mg of Omega 3. Keep refrigerated for freshness.

Hempseed is considered by leading researchers and medical doctors to be one of the most nutritious food sources on the planet. Shelled hempseed is packed with 33 percent pure digestible protein and is rich in iron and vitamin E as well as omega-3 and GLA. A recent report funded by the Canadian government states that hemp protein is comprised of 66 percent high-quality edistin protein, and that hempseed contains the highest percentage of this of any plant source. Hemp also contains three times the vitamin E contained in flax. Unlike soy, hemp is not genetically modified, and it doesn't contain the anti-nutritional qualities commonly found in soy.
they both also make excellent oils.