Clean and seal your grout perfectly with green chemicals

Grout is like teeth.  The two very effective cleaning agent is baking soda and hydrogen peroxide.  Dry or paste baking soda helps to polish away trapped dirt and especially grease.  Hydrogen peroxide bleaches.  I always know that.  If your grout is white for example, you can get back the original color as white as you want.  The problem is the amount of work and the amount of hydrogen peroxide to use.  Now I made it perfect.

First option.  You add first-aid 3% hydrogen peroxide slowly into baking soda powder.  You just add enough to "wet" all the powder and obtain a paste.  For horizontal surface you can make the paste thinner.  Now you just need to apply the paste on the grout.  The hydrogen peroxide will stick and bleach much longer than if you spray the liquid onto a vertical wall.  If helps if you brush the paste into the grooves to get rid some of the grease and dirt first.

You rinse or just wipe when dry.  Residue baking soda is eatable and safe.  Hydrogen peroxide turn into water and oxygen.  If your grout is white, the residue baking soda actually makes your grout look snow white.

Water tends to separate from the baking soda paste.  You can add something like a little guar gum or xathan gum to the mixture at room temperature to thicken and stabilize the mixture.  If you use corn starch, you probably have to warm or heat the hydrogen peroxide first to get a gel.

Option two.  Hydrogen peroxide plus acid is a bleach.  The hydrogen peroxide is more table is acid.  Citric acid crystal from food supplies is a good acid.  A one pound bag doesn't cost that much and last a very long time.  One teaspoon per cup of hydrogen peroxide (or water) is a stronger acid than vinegar.  You can make a much higher concentration acid until the crystals no longer dissolves.  Now you need to thicken the bleach to save peroxide.  It's a few dollars a quart but you have walls and walls of tile in the bathroom, kitchen or the floor.

I get the idea from computer preservation enthusiast.  They thicken peroxide to work on plastic shells of old computers.  I already told you.  The warm or heat the peroxide in the microwave.  Then add corn starch or other starch to make a gel of peroxide.  You can add guar gum or other gum in room temperature.  You save gums if you warm the peroxide too, and it works better.  You will use a lot less gum than starch.  Just don't add baking soda to the acid as it will react.

It's perfectly safe to heat the peroxide.  The peroxide will decompose faster but still in a slow rate compared to the bleaching.

In this option the ingredients are all natural and biodegradable.

Now the difficult part is sealing of the grouts once it is clean.  There are plenty of grout sealants to choose from if you don't mind the toxicity.  Pick one that whitens as well as sealing.  Then you don't need to worry whether the grouts are clean enough for sealing.  And you don't need to match the color of the grout in various shades of white.

I was wondering if there's anything naturally non-toxic for my kitchen counter?  Easy to apply but do not need to be permanent?

Simple - wax!  I actually tried before to use a candle to seal the grouts.  I gave up.  You cannot rub the candle wax into the grooves.  And you cannot melt the wax by burning the candle - too much soot.

Just happen I have emulsifying wax NF at hand so I tried.  You have to melt it and pour onto the grouts.  Then recover the excess wax that solidifies.  You cannot spread the wax easily because the tile will cool and solidify the wax.  It will have a lot of waste and inconvenient.

I have the almost perfect solution.  The wax comes in small peas.  You just put a pea on the grout and melt it with a gas lighter type barbeque lighter.  The wax will melt and follows the tip of the flame down the groove.  The wax stays white when solidifies.  You can use organic white bees wax if you want.  It's at even higher melting point.  This lighter method seems to be much better than direct pouring, when the wax solidifies as soon as it touch the cool surface.

Since grout is very porous, I doubt if you can easily get rid of all the wax.  Initially the whole groove is covered by wax.  It's unlikely you can melt the wax by any hot objects unless you pour boiling water on the wax.  How often does that happen?  If that happens you can "repair" the wax in no time.

So far the wax stays in the grooves, translucent white in deeper grooves.  When there is wax, no way can dirt get in there or stain the grout.

It's not a quick to seal with wax.  But it's pleasant and you can spread the work in as many stages as you want.  The area of the kitchen counter that you prepare food isn't that big.