“Are peanut shells made of wood?”

The peanut plant. (Image: Franz Eugen Köhler, Köhler’s Medizinal-Pflanzen, 1897 via Wikipedia)

One evening, while learning the fine art of peanut shell cracking, The Five-Year-Old naturally wanted to know more about the substance she was working with.

The Five-Year-Old: “Mommyo, are peanut shells made of wood?”

Not exactly, but peanut shells have quite a bit in common with wood. Both wood and peanut shells are made up primarily of cellulose and lignin.

Cellulose is a plant fiber mainly used in nature to build the primary cell walls of green plants (in other words — it’s the stuff that makes the plant grow). Not surprisingly, cellulose is the most abundant organic compound on Earth. Some 33% of all plant matter is cellulose (cotton contains 90% cellulose and wood 40-50%). Industry extracts the cellulose from plants to manufacture everyday products like paper, paperboard, nylon, and cellophane. Experiments are also underway to use cellulose as the foundation for alternative biofuels. Although our bodies can’t digest the cellulose in the plants we eat, we still manage to make good use of it. (Hint: You may be more used to thinking of the plant cellulose in your diet as fiber.)

Lignin works in conjunction with cellulose to provide strength and support to the plant’s cell walls (and to conduct water).  The more lignin a plant has, the woodier it feels. Lignin gives the branches, twigs, and trunks of woody plants their shape and structure. It provides the strength and durability to make woods like teak, oak, and pine useful to the furniture and construction industry. Unfortunately, it’s also the stuff that makes wood burn.

An answer on a Yahoo! message board says that the lignin to cellulose ratio for peanut shells is 79:100. By way of comparison, the lignin to cellulose ratio for a California Sequoia tree is 70:100, and for an oak tree 62:100. I was unable to find a secondary source to verify these ratios (at least in terms that I could understand), but if they are true, the relatively high concentration of lignin in peanut shells would explain their woody feel.

Related Links:

About Shala Howell

I spent two decades helping companies like Bell Labs, Juniper Networks, and a genetic testing company that was later acquired by CVS translate some of the world’s most complicated concepts into actionable, understandable English. Now I'm working on a much harder problem -- fostering children’s curiosity and engagement in the scientific, artistic, and linguistic world that surrounds them. The first book in my Caterpickles Parenting Series, What’s That, Mom?, focuses on how to use public art to nurture children’s curiosity in the world around them. My next book, Did Dinosaurs Have Belly Buttons?, is currently planned for release in 2018. In the meantime, you can find me blogging about life with a very curious Ten-Year-Old at Caterpickles.com, chatting about books and the writing life at BostonWriters.blog, and tweeting about books, writing, science, & things that make me smile at @shalahowell.
This entry was posted in Ask the iPhone, Nature and tagged , , , , . Bookmark the permalink.

One Response to “Are peanut shells made of wood?”

  1. This was fascinating! I didn’t know all of that, and I love learning cool things like this. Especially that Lignin makes wood woodier depending on the amount. I always thought it was just the cellulose. Very informative.

    Like

What are you thinking?

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s